Fast imaging of laser-blow-off plume:Lateral confinement in ambient environment

The dynamics of plasma plume, formed by the laser-blow-off of multicomponent LiF-C thin film under various ambient pressures ranging from high vacuum to argon pressure of 3 Torr, has been studied using fast imaging technique. In vacuum, the plume has ellipsoidal shape. With the increase in the ambient pressure, sharp plume boundary is developed showing a focusing-like confinement in the lateral space behavior in the front end, which persists for long times. At higher ambient pressure (> 10−1 Torr ), structures are developed in the plasma plume due to hydrodynamic instability/turbulences.

Influence of ambient gas on the temperature and density of laser produced carbon plasma

The effect of ambient gas on the dynamics of the plasma generated by laser ablation of a carbon target using 1.06 μm radiation from a Q-switched Nd:YAG laser has been investigated using a spectroscopic technique. The emission characteristics of the carbon plasma produced in argon, helium and air atmospheres are found to depend strongly on the nature and pressure of the surrounding gas. It has been observed that hotter and denser plasmas are formed in an argon atmosphere rather than in helium or air as an ambient.

Prompt electron emission and collisional ionization of ambient gas during pulsed laser ablation of silver

A silver target kept under partial vacuum conditions was irradiated with focused nanosecond pulses at 1:06 mm from a Nd:YAG laser. The electron emission monitored with a Langmuir probe shows a clear twin-peak distribution. The first peak which is very sharp has only a small delay and it indicates prompt electron emission with energy as much as 60 5 eV. Also the prompt electron emission shows a temporal profile with a width that is same as that for the laser pulse whereas the second peak is broader, covers several microseconds, and represents the low-energy electrons (2 0:5 eV) associated with the laser-induced silver plasma as revealed by time-of-flight measurements. It has been found that prompt electrons ejected from the target collisionally excite and ionize ambient gas molecules. Clearly resolved rotational structure is observed in the emission spectra of ambient nitrogen molecules. Combined with time-resolved spectroscopy, the prompt electrons can be used as excitation sources for various collisional excitation–relaxation experiments. The electron density corresponding to the first peak is estimated to be of the order of 1017 cm?--3 and it is found that the density increases as a function of distance away from the target. Dependence of probe current on laser intensity shows plasma shielding at high laser intensities.

Twin peak distribution of electron emission profile and impact ionization of ambient molecules during laser ablation of silver target

Laser-induced plasma generated from a silver target under partial vacuum conditions using the fundamental output of nanosecond duration from a pulsed Nd:yttrium aluminum garnet laser is studied using a Langmuir probe. The time of flight measurements show a clear twin peak distribution in the temporal profile of electron emission. The first peak has almost the same duration as the laser pulse while the second lasts for several microseconds. The prompt electrons are energetic enough ('60 eV) to ionize the ambient gas molecules or atoms. The use of prompt electron pulses as sources for electron impact excitation is demonstrated by taking nitrogen, carbon dioxide, and argon as ambient gases.

Effect of ambient gas on the expansion dynamics of plasma plume formed by laser blow off of thin film

A study has been carried out to understand the influence of ambient gases on the dynamics of laser-blow-off plumes of multi-layered LiF–C thin film. Plume images at various time intervals ranging from 100 to 3000 ns have been recorded using an intensified CCD camera. Enhancement in the plume intensity and change in size and shape occurs on introducing ambient gases and these changes are highly dependent on the nature and composition of the ambient gas used. Velocity of the plume was found to be higher in helium ambient whereas intensity enhancement is greater in argon environment. The plume shapes have maximum size at 10−2 and 10−1 Torr of Ar and He pressures, respectively. As the background pressure increases further (>10−2 Torr: depending on the nature of gas), the plume gets compressed/focused in the lateral direction. Internal structure formation and turbulences are observed at higher pressures (>10−1 Torr) in both ambient gases.

Una Aproximació a l'àrea de coneixement del medi natural, social i cultural des de la perspectiva d'identitat i diversitat

Aproximació a la part teòrica de la revisió de la tradició de l'estudi del medi, una nova proposta d'innovació pedagògica i l'experimentació del primer any

El medi marí del cap de Creus i el golf de Roses

El medi marí de cap de Creus i golf de Roses té unes característiques ecològiques, geològiques i oceanogràfiques excepcionals que han permès el desenvolupament turístic i pesquer de les viles costaneres adjacents, Aquest article sintetitza els principals valors ecològics i econòmics de l'àmbit marí d'aquests dos espais inclosos dins la candidatura de Patrimoni Mundial de la UNESCO

El Bosc de ribera, un medi a preservar

En aquest estudi fem un repás dels diferents tipus de boscos de ribera de les comarques gironines, descrivim els processos fluvio-torrencials que motiven l'acció antrópica i, finalment analitzem el cas concret del riu Onyar

Conèixer Alaró : aplicació didàctica a l'àrea de coneixement del medi a educació infantil i educació primària.'Conocer Alaró : aplicación didáctica del área de conocimiento del medio en Educación Infantil y Educación Primaria'.

Resumen tomado de la publicación

Promoció i educació per a la salut en el medi escolar : les escoles promotores de salut. 'Promoción i educación para la salud en el medio escolar : las escuelas promotoras de salud'.

Resumen tomado del autor

La grimpada i l'escalada : continguts del bloc d'activitats en el medi natural f??cilment aplicables dins el marc escolar

Resumen tomado del autor. Se muestran fotograf??as

Exercicis per a l'entrenament de la musculatura flexora del tronc en el medi aqu??tic

Resumen tomado del autor. Contiene tablas explicativas de ejercicios, descripci??n de ejercicios con im??genes y tablas de resultados

Orientaci?? a peu i en bicicleta : un mitj?? per treballar l'orientaci?? al medi natural i alhora promocionar la utilitzaci?? de la bicicleta a l'ESO

Resumen tomado de la publicaci??n. Contiene fotograf??as, plantilla de itinerarios, mapa de la situaci??n geogr??fica del IES e im??genes del libro de ruta

La cartografia i l'orientació, eines bàsiques en la didàctica de l'àrea de coneixement del medi. 'La cartografía y la orientación, herramientas básicas en la didáctica del área de conocimiento del medio'.

Debido a la vinculación actual entre la geografía, los principales conflictos mundiales y los medios de comunicación, la educación debe preparar al alumnado para conocer y actuar de forma positiva en el medio o entorno en el que vive. El currículum de las Islas Baleares así lo contempla. Para conseguirlo es fundamental poder conceptualizar el espacio y el tiempo y para ello son necesarias las herramientas cartográficas y la capacidad de orientación en un espacio real utilizando mapas y planos. Se presentan algunas estrategias como los itinerarios personales, la lectura y aplicación didáctica de planos y mapas, y se comenta la necesidad de evaluar estos recursos.