Dynamics of free-running, pump-modulated and coupled semiconductor and solid-state lasers

The output of a laser is a high frequency propagating electromagnetic field with superior coherence and brightness compared to that emitted by thermal sources. A multitude of different types of lasers exist, which also translates into large differences in the properties of their output. Moreover, the characteristics of the electromagnetic field emitted by a laser can be influenced from the outside, e.g., by injecting an external optical field or by optical feedback. In the case of free-running solitary class-B lasers, such as semiconductor and Nd:YVO4 solid-state lasers, the phase space is two-dimensional, the dynamical variables being the population inversion and the amplitude of the electromagnetic field. The two-dimensional structure of the phase space means that no complex dynamics can be found. If a class-B laser is perturbed from its steady state, then the steady state is restored after a short transient. However, as discussed in part (i) of this Thesis, the static properties of class-B lasers, as well as their artificially or noise induced dynamics around the steady state, can be experimentally studied in order to gain insight on laser behaviour, and to determine model parameters that are not known ab initio. In this Thesis particular attention is given to the linewidth enhancement factor, which describes the coupling between the gain and the refractive index in the active material. A highly desirable attribute of an oscillator is stability, both in frequency and amplitude. Nowadays, however, instabilities in coupled lasers have become an active area of research motivated not only by the interesting complex nonlinear dynamics but also by potential applications. In part (ii) of this Thesis the complex dynamics of unidirectionally coupled, i.e., optically injected, class-B lasers is investigated. An injected optical field increases the dimensionality of the phase space to three by turning the phase of the electromagnetic field into an important variable. This has a radical effect on laser behaviour, since very complex dynamics, including chaos, can be found in a nonlinear system with three degrees of freedom. The output of the injected laser can be controlled in experiments by varying the injection rate and the frequency of the injected light. In this Thesis the dynamics of unidirectionally coupled semiconductor and Nd:YVO4 solid-state lasers is studied numerically and experimentally.

"Do Not Celebrate Your Feast without Your Neighbours" : A Study of References to Feasts and Festivals in Non-Literary Documents from Ramesside Period Deir el-Medina

This dissertation is a study of the forms and functions of feasts and feasting in the ancient Egyptian village of Deir el-Medina in Thebes (modern Luxor). This particular village, during the New Kingdom (c. 1550 1069 BC), was inhabited by the men (and their families) who constructed the Royal Tombs in the Valley of the Kings and the Valley of the Queens. The royal artisans were probably more literate than the average Egyptians and the numerous Ramesside Period (c. 1295 1069 BC) non-literary texts found in the excavations of the village and its surroundings form the source material for this study. In this study, the methods used are mainly Egyptological and the references to feasts and feasting are considered in view of what is known of New Kingdom Egypt, Thebes, and Deir el-Medina. Nevertheless, it is the use of the methodological concept local vernacular religion that has resulted in the division of the research findings into two sections, i.e., references to feasts celebrated both in and outside the community and other references to feasts and feasting in the village. When considering the function of the feasts celebrated at Deir el-Medina, a functional approach to feasts introduced by anthropologists and archaeologists is utilized. The Deir el-Medina feasts which were associated with the official religion form a festival calendar of feasts celebrated annually on the same civil calendar day. The reconstructed festival calendar of Deir el-Medina reflects the feasts celebrated around Thebes or, at least, in Western Thebes. The function of the nationally and regionally observed feasts (which, at least at Deir el-Medina, resulted in a work-free day) may have been to keep people content so that they would continue to work which was to the advantage of the king and the elite surrounding him. Local feasts appear to have been observed more irregularly at Deir el-Medina or perhaps according to the lunar calendar. Feasts celebrated by the community as a whole served to maintain the unity of the group. In addition to feasts celebrated by the entire community, the inhabitants of Deir el-Medina could mark their own personal feasts and organize small gatherings during public feasts. Through such feasts, an individual man might form alliances and advance his chances of a favourable marriage or of acquiring a position on the work crew.

Original Pirate Material : Translating Justin Somper's Demons of the Ocean

Tutkielma käsittelee suomentamani Vampiraatit: Kirottujen laiva -nuortenromaanin käännösprosessia. Materiaalina on kustantajalle toimittamani näytekäännös, joka käsittää yhden kokonaisen luvun ja lisäksi kirjan tapahtumiin keskeisesti liittyvän runon. Molemmista tarkastellaan sekä lopullisia, julkaistuja versioita että ensimmäisiä raakaversioita. Julkaistut versiot ovat osa varsinaista tutkielmaa, raakaversiot ja lähtötekstit puolestaan on sisällytetty mukaan liitteinä. Tarkastelunäkökulmani on pääosin deskriptiivinen ja kontrastiivinen. Proosa-analyysi jakautuu kahteen osaan. Ensimmäisessä osassa tutkin tapoja, joilla käännökseni vastustaa ns. lisääntyvän standardisoitumisen lakia (the law of growing standardization), jota Gideon Toury on ehdottanut yleispäteväksi käännöslaiksi. Touryn laki ennustaa, että käännökset ovat useimmiten tyylillisesti alkuteoksiaan latteampia. Esimerkkini kuitenkin osoittavat, että kääntäjän on mahdollista valita ratkaisunsa niin, että latistumiselta vältytään, ainakin silloin, kun lähtöteksti on melko suoraviivaista. Proosa-analyysin jälkimmäinen osa keskittyy käännöksen muokkaamiseen. Vertaan siinä näytekäännös-luvun ensimmäistä versiota julkaistuun versioon ja tutkin muun muassa sitä, missä määrin ensimmäinen versio sisältää lähtökielen interferenssiä, ts. missä määrin englannille tyypilliset rakenteet paistavat siitä läpi. Tarkastelun kohteena ovat myös kohdekieliset kömpelyydet ja niiden poistaminen sekä pienet mutta kokonaisuuden kannalta tärkeät tyylilliset muutokset. Esimerkeistä käy selvästi ilmi kääntämisen prosessimainen luonne. Käännösnäytteeseen sisältyneen runon suomentaminen oli oma erillinen kokonaisuutensa. Tässä osiossa vertailen lähtötekstiä, raakaversiota ja julkaistua käännöstä rinnakkain säkeistö säkeistöltä. Tarkastelussa painottuvat edelleen tekstin muokkaaminen ja hiominen. Analyysien taustaksi esittelen lyhyesti alkuteoksen ja sen kirjoittajan Justin Somperin. Kuvailen myös omaa käännösfilosofiaani ja esittelen kaksi siihen voimakkaasti vaikuttanutta suomentajaa.

Det pedagogiska självet : en narrativ studie av direktvalda svensklärarstudenters berättelser

The Pedagogical Self: a narrative study of stories by prospective subject teachers of Swedish The aim of this study is to examine how prospective subject teachers of Swedish experience themselves, their lives and their studies in university context. By answering this question I try to shed light on the pedagogical self of the students, i.e. to reach a deeper understanding of the narrative construction of their teacher identity. My material consists of stories written by one group of students and of transcribed interviews with another group of students at Nordica. All these students have entered both the teacher education programme and studies in their major subject simultaneously, through the so called direct admission. My study focuses on the students first year at the university. I define teacher identity, the pedagogical self, as the part of an individual s self-concept where he/she makes an assessment of himself/herself as a teacher(-to-be). The frame of reference of this interdisciplinary narrative study is founded on phenomenology, hermeneutics, social constructionism and dialogism. The main analysis of the stories is thematic, with the addition of linguistic and metaphorical analysis. With reference to the theories of Paul Ricoeur and Katharine Young, I regard the textual world of the stories as a world of its own. This implies that the researcher can feel free to concentrate on the texts, thus being able to leave the mental processes of the writers disregarded. The theoretician that has influenced my research the most is Max van Manen. He combines a pedagogical attitude with a phenomenological-hermeneutic philosophy. My research results imply that most of these students are drawn to studying Swedish by the clear professional orientation of the studies; their identity as teachers seems to be stronger than their identity as language teachers. The image of a teacher is relatively traditional: a teacher is seen as a self-evident authority, but at the same time as a fostering educator. The students see their studies in a larger perspective: studies as well as the future profession are only one part of life, albeit an important one. Keywords: narrativity, teacher identity

Keskustelu yliopiston uudesta palkkausjärjestelmästä - akateemisten arvojen murtaja vai toiveiden täyttäjä?

There has been a change in university´s position in society during the last of decades from traditional university to result-based university. Result-based is considered as a steering mechanism. The context in this study is the period when the New Salary System was introduced. In the New Salary System salary is based on the performance appraisal made by the supervisor. The purpose of the study was to understand the discussion of the New Salary System and how this discussion should be interpreted. The research task had two parts. In the first part the objective was to identify how the academic work was conceptualised. In the second part I analyzed how one related to the New Salary System and how this was interpreted in relation to representation of academic work. The research material consisted of webblogs from the year 2005. Webblogs were located in the internet and one had free access to them. Mostly employees from Finnish universities wrote to them. Besides the salary system writers discussed the university and the academic work. Two different ways of talking about the academic work were found in research material. In the first one the academic work was based on community and in the second one on individuality. When community was emphasized writers discussed also science and research and academic traditions such as peer review. When individuality was emphasized writers discussed individual performance and the importance of salary according to one´s performance. The analysis shows that the New Salary System was opposed and supported. Opposition was based on arguments for the traditional university; peer review, truth, academic profession, academic community and university’s autonomy are the most important arguments. Supporters used arguments such as the need to make individual´s performance visible and breaking the existing power structures.

Koko talo soi : Klemetti-Opisto suomalaisen musiikkikulttuurin kehittäjänä 1953-1968

This study aims to examine the operations and significance of the Klemetti Institute (Klemetti-Opisto) as a developer of Finnish music culture from 1953 to 1968 during the term of office of the Institute s founder and first director, Arvo Vainio. The Klemetti Institute was originally established as a choir institute, but soon expanded to offer a wide range of music courses. In addition to providing courses for choir leaders and singers, the Institute began its orchestral activities as early as the mid-1950s. Other courses included ear training seminars as well as courses for young people s music instructors and in playing the kantele (a Finnish string instrument) and solo singing. More than 20 types of courses were offered over the 16-year period. The Klemetti Institute s courses were incorporated into the folk high school courses offered by the Orivesi Institute (Oriveden Opisto) and were organised during the summer months of June and July. In addition to funding based on the Folk High School Act, financial assistance was obtained from various foundations and funds, such as the Wihuri Foundation. This study is linked to the context of historical research. I examine the Klemetti Institute s operations chronologically, classifying instruction into different course types, and analyse concert activities primarily in the section on the Institute s student union. The source material includes the Klemetti Institute archives, which consist of Arvo Vainio s correspondence, student applications, register books and cards, journals and student lists, course albums and nearly all issues of the Klemettiläinen bulletin. In addition, I have used focused interviews and essays to obtain extensive data from students and teachers. I concentrate on primary school teachers, who accounted for the majority of course participants. A total of more than 2,300 people participated in the courses, nearly half of whom took courses during at least two summers. Primary school teachers accounted for 50% to 70% of the participants in most courses and constituted an even larger share of participants in some courses, such as the music instructor course. The Klemetti Institute contributed to the expansion throughout Finland of a new ideal for choral tone. This involved delicate singing which strives for tonal purity and expressiveness. Chamber choirs had been virtually unheard of in Finland, but the Klemetti Institute Chamber Choir popularised them. Chamber choirs are characterised by an extensive singing repertoire ranging from the Middle Ages to the present. As the name suggests, chamber choirs were originally rather small mixed choirs. Delicate singing meant the avoidance of extensive vibrato techniques and strong, heavy forte sounds, which had previously been typical of Finnish choirs. Those opposing and shunning this new manner of singing called it ghost singing . The Klemetti Institute s teachers included Finland s most prominent pedagogues and artists. As the focused essays, or reminiscences as I call them, show, their significance for the students was central. I examine extensively the Klemetti Institute s enthusiastic atmosphere, which during the early years was characterised by what some writers described as a hunger for music . In addition to distributing a new tonal ideal and choir repertoire, the Klemetti Institute also distributed new methods of music education, thus affecting the music teaching of Finnish primary schools, in particular. The Orff approach, which included various instruments, became well known, although some of Orff s ideas, such as improvisation and physical exercise, were initially unfamiliar. More important than the Orff approach was the in-depth teaching at the Klemetti Institute of the Hungarian ear training method known as the Kodály method. Many course participants were among those launching specialist music classes in schools, and the method became the foundation for music teaching in many such schools. The Klemetti Institute was also a pioneer in organising orchestra camps for young people. The Klemetti Institute promoted Finnish music culture and played an important role in the continuing music education of primary school teachers. Keywords: adult education, Grundtvigian philosophy, popular enlightenment, Klemetti Institute, Kodály method, choir singing, choir conducting, music history, music education, music culture, music camp, Orff approach, Orff-Schulwerk, Orivesi Institute, instrument teaching, free popular education, communality, solo singing, voice production

Nuorten hyvinvointi, opiskelu ja opinto-ohjaus erityisen koulutustehtävän saaneessa lukiossa

This is a case-study of students well-being studying in Sibelius Upper Secondary School which has got a special educational task in dance and music. The first purpose of this study is to analyse the students well-being, motivation, studying satisfaction and try to find out what kind of problems the students meet when studying in Upper Secondary School. The second purpose of this study is to try find means in counselling to help students in their Upper Secondary School Studies. The data were gathered in three parts. The first questioning was based on Allardt s (1976; 1998) well-being theory. In this questioning (N = 187) the students described their satisfaction in having (material things), loving (social relationships) and being (free time). The second data was collected by interviews (N = 19). The third data is a follow-up questioning (N = 10) for graduated students. The whole data was analysed with qualitative methods. The gathered qualitative data were compared with the quantitative data gathered by the National Institute for Health and Welfare. Results of this study indicate that the students in this case-study are mainly satisfied with their well-being, social and material things in their studying environment including counselling and teaching. The research results show that some of the students are exhausted due too muchtime spent in studying. This was verified also in the quantitative data gathered by the National Institute for Health and Welfare. These students suffer for the lack of free time and rest. Students who are motivated and have reached the autonomous way of studying do better in their Upper Secondary School Studies than those who study in unautonomous way.A quite wide range of students tend to make individual studying programmes and spend four or more years in Upper Secondary School instead of the three year programme. The individual programme gives them more time for practicing their special skills in the field of the school s special educational task and to give themselves more time for studying the basic subjects of the Upper Secondary School. Some of the students who tend to take extra years in Upper Secondary School have difficulties in their studying skills and are unsure of their studying motivation. The competition among students in Upper Secondary School with the special educational task causes stress and exhaustion for some of the studied students. These students have difficulties with integrating themselves into the social environment. For the other students the school s social environment works as a motivator for their studies and increases their well-being in their studies. According to the results of the follow-up questioning in this study the students value most the network with the other students they made while studying at the Sibelius Upper Secondary School. According to this study the students would need more counselling in all stages of their Upper Secondary School Studies. The autonomous students do quite well in their studies despite of the small amount of given counselling. They would also need more counselling in planning their further studies after Upper Secondary School. The biggest challenges to student counselling in Sibelius Upper Secondary School are helping the students to find their individual ways of studying and helping them to learn the ways of autonomous studying skills. Keywords: Upper Secondary School with a special educational task, well-being, talent, Upper Secondary School, Young person in Upper Secondary School, motivation, counselling, studying

Rakkaat vanhemmat? : Perheen merkityksestä erityisluokan oppilaalle

The aim of this study was to find out the meaning family has for a pupil who studies in a special class, or how important family is for the pupil s emotional life, the development of his self-confidence, freetime activities, attitudes on school, plans for further studies and his general social development. The theoretical base of this study was formed by social scientists' theories on postmodern family, which is due to urbanization and urban life style, and theories on family pluralism, the powerful effects that changes in family life have on pupils in special education, the weak self-confidence and low sosioeconomic background among those pupils and the effects of family's sosioeconomic status on pupil's willingness to get education or the theory on the accumulation of education. Study problems were set in the direction determined by these theories and in order to study the accurateness of the theories. The method used in the study was theme interview, which is sometimes also called half-structured interview. The material for the study was collected in October 1998 in a special school in Helsinki. The material contains answers given by pupils in theme interviews and background information about pupils' families, which where collected from the pupils' parents by mail. Content analysis was used to analyze the material. The study showed that it is very important to pupils' attitudes on school and their self-confidence that their families are entire and that the families give them support. The children, whose parents are interested in school education and discuss a lot about things, seem to have positive attitudes on school and good self-confidence, too. The parental support also has an effect on how the pupils spend their free time and on their hobbies, too. Obviously the families have quite an important meaning for pupils in special class, but if the families don t support them, the consequence is problems particularly for the development of self-confidence. The theory on the low sosioeconomic background among students in special education gets support from this study, but nothing can be said about it's effect on further studies. On account of the results it can be suggested that special schools must arrange occasions where the pupils' parents are clearly informed about the important meaning of their support for the pupils studies and the development of the pupils' self-confidence. The most important sources for the theoretical background were the books written by Jallinoja, Kivinenand Rinne, Moberg, Scanzoni and P. Takala. The most important sources for the method were the books written by Hirsjärvi and Hurme and Pietilä. Keywords: family, special class, pupil in special education, support, self-confidence, postmodern family

Tekstiilikulttuurisen lukutaidon edistäminen museoissa

Purpose: The study focuses on the question, how to advance textile cultural interpretation skills in museum. The theme was actual, because there have been many workshops in different kind of museums, which have raised textile into important role of their museum pedagogy. The knowing of nature of textile materials was highlighted in former studies as the most crucial thing in craft. That is reason for choosing textile to study. The theoretical approach of study was particularized to the meanings which have been given to craft during recent ten years. Furthermore the composition of textile culture and transmitting textile cultural heritage were examined throug the theory. The finnish museum as a place for learning, as well as the contens of museum pedagogy, were analyzed. The fundamental approach to study was cultural research and art education. Methods: The methodological approach was theory-based theme interview. Before interviewing informants the charting was made by using literature, interviews and observation, to find out the most important themes within subject. Specialists were interviewed personally and results were sent to them by e-mail for further comments. There were 8 informants and they were chosen with intentional sampling from different kind of museums, from teacher education and among craft teachers. Research material was analyzed with content analysis by using deductive reasoning. Conclusions: The study revealed that there are three strategies in advancing textile cultural interpretation. The most remarkable strategies are 1) making acquaintance of materials and working with them, 2) getting exiting events with posibilities to use one s whole body and 3) getting textile cultural knowledge by using for example discovery - style learning. In practice those strategies were mixed, which also was considered advisable. Another conclusion the study revealed, is the desirable, acceptable attitude not only to the craft with creative, free beginning but also to the craft made like its model in museum. Learning from model can be felt as a very moving experience, like a journey in time. The side result of the study was the importance of collaboration of museums and schools in advancing textile cultural interpretation skills as well as significance of using internet in collaboration and relations.

Drug Analysis without Primary Reference Standards : Application of LC-TOFMS and LC-CLND to Biofluids and Seized Material

Drug Analysis without Primary Reference Standards: Application of LC-TOFMS and LC-CLND to Biofluids and Seized Material Primary reference standards for new drugs, metabolites, designer drugs or rare substances may not be obtainable within a reasonable period of time or their availability may also be hindered by extensive administrative requirements. Standards are usually costly and may have a limited shelf life. Finally, many compounds are not available commercially and sometimes not at all. A new approach within forensic and clinical drug analysis involves substance identification based on accurate mass measurement by liquid chromatography coupled with time-of-flight mass spectrometry (LC-TOFMS) and quantification by LC coupled with chemiluminescence nitrogen detection (LC-CLND) possessing equimolar response to nitrogen. Formula-based identification relies on the fact that the accurate mass of an ion from a chemical compound corresponds to the elemental composition of that compound. Single-calibrant nitrogen based quantification is feasible with a nitrogen-specific detector since approximately 90% of drugs contain nitrogen. A method was developed for toxicological drug screening in 1 ml urine samples by LC-TOFMS. A large target database of exact monoisotopic masses was constructed, representing the elemental formulae of reference drugs and their metabolites. Identification was based on matching the sample component s measured parameters with those in the database, including accurate mass and retention time, if available. In addition, an algorithm for isotopic pattern match (SigmaFit) was applied. Differences in ion abundance in urine extracts did not affect the mass accuracy or the SigmaFit values. For routine screening practice, a mass tolerance of 10 ppm and a SigmaFit tolerance of 0.03 were established. Seized street drug samples were analysed instantly by LC-TOFMS and LC-CLND, using a dilute and shoot approach. In the quantitative analysis of amphetamine, heroin and cocaine findings, the mean relative difference between the results of LC-CLND and the reference methods was only 11%. In blood specimens, liquid-liquid extraction recoveries for basic lipophilic drugs were first established and the validity of the generic extraction recovery-corrected single-calibrant LC-CLND was then verified with proficiency test samples. The mean accuracy was 24% and 17% for plasma and whole blood samples, respectively, all results falling within the confidence range of the reference concentrations. Further, metabolic ratios for the opioid drug tramadol were determined in a pharmacogenetic study setting. Extraction recovery estimation, based on model compounds with similar physicochemical characteristics, produced clinically feasible results without reference standards.

Prolamin degradation in sourdoughs

This thesis examines protein behaviours that occur during cereal fermentations. The focus is on the prolamin degradation in sourdoughs. The thesis also looks at what happens to the oat globulins during an oat bran acidification process. The cereal prolamins are unique proteins in many respects. The wheat prolamins (glutenins and gliadins) are responsible for the formation of the gluten that provides the viscoelastic properties to wheat doughs whereas the rye prolamins (secalins) are unable to develop gluten-like structures. In addition, many baking technological features, such as flavour, shelf-life and dough properties are affected by the protein degradation that might occur during processing. On the other hand, the prolamins contain protein structures that are harmful to gluten sensitive people. It is thus evident that the degradation of the prolamins in sourdough processes may be approached from various aspects. This thesis describes some of these approaches. Four different cereal fermentations were carried out. Wheat sourdough (WSD) and rye sourdough (RSD) fermentations represented traditional sourdoughs. A germinated-wheat sourdough (GWSD) was a novel sourdough type that was prepared using germinated wheat grains that had high and diverse proteolytic activities. The oat bran fermentation (OBF) represented a fermentation system that lacked functional cereal proteases. The high molecular weight glutenins and rye secalins were degraded during the WSD and RSD fermentations, respectively. It was noteworthy that in WSD only a very limited degradation of the gliadins occurred. The gliadins were, however, hydrolysed very extensively during the GWSD fermentation. No protein degradation was observable in the OBF system. Instead the acidification altered the solubility of the oat globulins and this finally led to their aggregation. This thesis confirms that the endogenous proteases of cereals hydrolyse cereal prolamins in sourdoughs. The thesis also shows that the proteolytic activity of the used cereal raw material determines the extent of proteolysis that occurs in sourdough. This means that bakers may adjust the protein degradation in their sourdoughs by selecting the raw material based on its proteolytic activity. The thesis also demonstrates that by using germinated grains, with high and diverse proteolytic activity in sourdough preparations, the prolamins can be extensively degraded. Whether such highly proteolytic food technology could be used to manufacture new gluten-free cereal-based products for gluten sensitive people remains to be solved.

TlBr raw material purification, crystal growth, annealing, detector fabrication and characterisation for gamma-ray detector applications

The research reported in this thesis dealt with single crystals of thallium bromide grown for gamma-ray detector applications. The crystals were used to fabricate room temperature gamma-ray detectors. Routinely produced TlBr detectors often are poor quality. Therefore, this study concentrated on developing the manufacturing processes for TlBr detectors and methods of characterisation that can be used for optimisation of TlBr purity and crystal quality. The processes under concern were TlBr raw material purification, crystal growth, annealing and detector fabrication. The study focused on single crystals of TlBr grown from material purified by a hydrothermal recrystallisation method. In addition, hydrothermal conditions for synthesis, recrystallisation, crystal growth and annealing of TlBr crystals were examined. The final manufacturing process presented in this thesis deals with TlBr material purified by the Bridgman method. Then, material is hydrothermally recrystallised in pure water. A travelling molten zone (TMZ) method is used for additional purification of the recrystallised product and then for the final crystal growth. Subsequent processing is similar to that described in the literature. In this thesis, literature on improving quality of TlBr material/crystal and detector performance is reviewed. Aging aspects as well as the influence of different factors (temperature, time, electrode material and so on) on detector stability are considered and examined. The results of the process development are summarised and discussed. This thesis shows the considerable improvement in the charge carrier properties of a detector due to additional purification by hydrothermal recrystallisation. As an example, a thick (4 mm) TlBr detector produced by the process was fabricated and found to operate successfully in gamma-ray detection, confirming the validity of the proposed purification and technological steps. However, for the complete improvement of detector performance, further developments in crystal growth are required. The detector manufacturing process was optimized by characterisation of material and crystals using methods such as X-ray diffraction (XRD), polarisation microscopy, high-resolution inductively coupled plasma mass (HR-ICPM), Fourier transform infrared (FTIR), ultraviolet and visual (UV-Vis) spectroscopy, field emission scanning electron microscope (FESEM) and energy-dispersive X-ray spectroscopy (EDS), current-voltage (I-V) and capacity voltage (CV) characterisation, and photoconductivity, as well direct detector examination.

The kinetics and reactivity of several polyatomic free radicals in reactions with NO2, O2, Cl2, and HCl

In this thesis, the kinetics of several alkyl, halogenated alkyl, and alkenyl free radical reactions with NO2, O2, Cl2, and HCl reactants were studied over a wide temperature range in time resolved conditions. Laser photolysis photoionisation mass spectrometer coupled to a flow reactor was the experimental method employed and this thesis present the first measurements performed with the experimental system constructed. During this thesis a great amount of work was devoted to the designing, building, testing, and improving the experimental apparatus. Carbon-centred free radicals were generated by the pulsed 193 or 248 nm photolysis of suitable precursors along the tubular reactor. The kinetics was studied under pseudo-first-order conditions using either He or N2 buffer gas. The temperature and pressure ranges employed were between 190 and 500 K, and 0.5 45 torr, respectively. The possible role of heterogeneous wall reactions was investigated employing reactor tubes with different sizes, i.e. to significantly vary the surface to volume ratio. In this thesis, significant new contributions to the kinetics of carbon-centred free radical reactions with nitrogen dioxide were obtained. Altogether eight substituted alkyl (CH2Cl, CHCl2, CCl3, CH2I, CH2Br, CHBr2, CHBrCl, and CHBrCH3) and two alkenyl (C2H3, C3H3) free radical reactions with NO2 were investigated as a function of temperature. The bimolecular rate coefficients of all these reactions were observed to possess negative temperature dependencies, while pressure dependencies were not noticed for any of these reactions. Halogen substitution was observed to moderately reduce the reactivity of substituted alkyl radicals in the reaction with NO2, while the resonance stabilisation of the alkenyl radical lowers its reactivity with respect to NO2 only slightly. Two reactions relevant to atmospheric chemistry, CH2Br + O2 and CH2I + O2, were also investigated. It was noticed that while CH2Br + O2 reaction shows pronounced pressure dependence, characteristic of peroxy radical formation, no such dependence was observed for the CH2I + O2 reaction. Observed primary products of the CH2I + O2 reaction were the I-atom and the IO radical. Kinetics of CH3 + HCl, CD3 + HCl, CH3 + DCl, and CD3 + DCl reactions were also studied. While all these reactions possess positive activation energies, in contrast to the other systems investigated in this thesis, the CH3 + HCl and CD3 + HCl reactions show a non-linear temperature dependency on the Arrhenius plot. The reactivity of substituted methyl radicals toward NO2 was observed to increase with decreasing electron affinity of the radical. The same trend was observed for the reactions of substituted methyl radicals with Cl2. It is proposed that interactions of frontier orbitals are responsible to these observations and Frontier Orbital Theory could be used to explain the observed reactivity trends of these highly exothermic reactions having reactant-like transition states.