Kinetic isotope effects of proton transfer reaction for amines by ultrasonic relaxation methods: Unexpected evidence from the results in ethylamine solutions

Ultrasonic absorption coefficients for ethylamine in heavy water (D2O) and in light water (H2O) have been measured in the frequency range from 0.8 to 220 MHz at 25 degrees C. A single relaxational process has been observed in these two kinds of solutions. From the concentration dependence of the ultrasonic relaxation parameters, and following the reaction mechanism proposed by Eigen et al. for ethylamine in H2O, the causes of the relaxations have been attributed to a perturbation of an equilibrium associated with a deuteron or proton transfer reaction. The rate and equilibrium constants have been estimated from deuterioxide or hydroxide ion concentration dependence of the relaxation frequency, and the kinetic isotope effects have been determined. In addition, the standard volume changes of the reactions have been calculated from the concentration dependence of the maximum absorption per wavelength, and the adiabatic compressibility has also been determined from the density and sound velocity for ethylamine in D2O and in H2O, respectively. These results are compared with those for propylamine and butylamine and are discussed in relation to the different kinetic properties between D2O and H2O, the reaction radii derived by Debye theory, and the structural properties of the reaction intermediate.

First-principles study of ferroelectricity and isotope effects in H-bonded KH2PO4 crystals

By means of extensive first-principles calculations we studied the ferroelectric phase transition and the associated isotope effect in KH2PO4 (KDP). Our calculations revealed that the spontaneous polarization of the ferroelectric phase is due to electronic charge redistributions and ionic displacements which are a consequence of proton ordering, and not vice versa. The experimentally observed double-peaked proton distribution in the paraelectric phase cannot be explained by a dynamics of only protons. This requires, instead, collective displacements within clusters that include also the heavier ions. These tunneling clusters can explain the recent evidence of tunneling obtained from Compton scattering measurements. The sole effect of mass change upon deuteration is not sufficient to explain the huge isotope effect. Instead, we find that structural modifications deeply connected with the chemistry of the H bonds produce a feedback effect on tunneling that strongly enhances the phenomenon. The resulting influence of the geometric changes on the isotope effect agrees with experimental data from neutron scattering. Calculations under pressure allowed us to analyze the issue of universality in the disappearance of ferroelectricity upon compression. Compressing DKDP so that the distance between the two peaks in the deuteron distribution is the same as for protons in KDP, corresponds to a modification of the underlying double-well potential, which becomes 23 meV shallower. This energy difference is what is required to modify the O-O distance in such a way as to have the same distribution for protons and deuterons. At the high pressures required experimentally, the above feedback mechanism is crucial to explain the magnitude of the geometrical effect.

ALTERNATIVE ROUTES TO DEUTERATION IN DARK CLOUDS

We investigate new approaches to the deuteration of C3H2, HC3N and HC5N in dark clouds, following the suggestion that protonated HC3N might form different isomers, a linear structure (HC3NH+) being the most stable. We consider the effect of linear HC3NH+ and HC5NH+ on the formation of HC3N and HC5N, and find that deuteration ratios at approximately 10 K are reduced, in the case of HC3N to values significantly below those observed, such that a deuteration mechanism other than direct deuteron transfer is probably required for cold clouds.

Characterisation of deuterium spectra from laser driven multi-species sources by employing differentially filtered image plate detectors in Thomson spectrometers

A novel method for characterising the full spectrum of deuteron ions emitted by laser driven multi-species ion sources is discussed. The procedure is based on using differential filtering over the detector of a Thompson parabola ion spectrometer, which enables discrimination of deuterium ions from heavier ion species with the same charge-to-mass ratio (such as C^{6 +}, O^{8 +}, etc.). Commonly used Fuji Image plates were used as detectors in the spectrometer, whose absolute response to deuterium ions over a wide range of energies was calibrated by using slotted CR-39 nuclear track detectors. A typical deuterium ion spectrum diagnosed in a recent experimental campaign is presented, which was produced from a thin deuterated plastic foil target irradiated by a high power laser.

Biblia sacra, pars.

BIBLIA SACRA

Vetus Testamentum, pars.

Avec quelques prologues et « capitula ». Genesis (sans prologue), avec « capitula » incomplets du début (1) ; Exodus (22) ; Levit. (40) ; Numeri (52) ; Deuteron. (69v) ; Josue (86v) ; Judices (97v) ; Ruth (109v) ; Reg. I-III,XI,38 (112) ; Isaias (150) ; Jeremias (175) ; Jeremiae Lament. et Oratio (209, 212) ; Ezechiel V,3-XIII,6 (213).

Biblia Sancti Martialis Lemovicensis, pars. I

Deuteron. (2) ; Josue (14) ; Judices (22v) ; Ruth, I,1-22 (31v) ; Isaias (32) ; Jeremias (48v) ; Jeremiae Lament. et Oratio jusqu'au v. 3 (66v, 67v) ; Ezechiel, III, 17, etc. (68) ; Daniel, I, 1-XIV, 19 (84) ; XII Proph. min. depuis Os., IV, 9, etc. (90) ; Job (104) ; Psalmi, I,1-LXXXVII,11 (112). En marge des ff. 109v-110 et 118v, prières (XIIIe-XIVe s.) : « Domine Deus omnipotens, qui es trinus... », « Mane intende ad me... »

Vetus Testamentum, pars.

Genesis I,29-L,25 (avec l'Épître de S. JEROME incomplète de la fin) (4) ; Exodus (27) ; Levit. (49) ; Numeri (63v) ; Deuteron. (85) ; Josue cum prol. (105, 106) ; Judices (121) ; Ruth (134v).

Biblia Sancti Martialis Lemovicensis altera. I

Genesis (5v) ; Exodus (25v) ; Levit. (41) ; Numeri (52) ; Deuteron. (67v) ; Josue (82) ; Judices (91) ; Ruth (101v) ; Isaias (103) ; Jeremias (122v) ; Jeremiae Lament. et Oratio (146, 148) ; Ezechiel (149) ; Daniel (171) ; XII Proph. min. (180) ; Job (198) ; Psalmi (208v).

Vetus Testamentum, pars.

Ce volume a été relié avec le BnF, Ms., Latin 104 pour former une bible complète, mais il semble que ces deux manuscrits ont été réalisés séparément, à une date et par un atelier différent. F. B, plusieurs notes du XIIIe siècle de mains différentes : au centre du feuillet : "Anno MCIII (sic) setagesimo IIII fu la fami per tutto lu mundu, et vauze lu tumenu de lu granu tr. XII" ; "Pahnutius humilis servus vestre sanctitatis".Au bas du feuillet : "Pahnutius humilis servus vestre sanctitatis" ; "Religioso viro venerabili abbati Santi Stephani de Nemore, salutem in Domino" ; "apnutius". F. 1, titre du XIIIe siècle : "Incipit epistula sancti Jeronimi presbiteri ad Paulinum de studio Scripturarum." Le manuscrit contient : Genesis (4) ; Exodus (20v) ; Levit. (34) ; Numeri (44v) ; Deuteron. (59) ; Josue (73) ; Judices (81v) ; Ruth (90) ; Reg. I-IV (91) ; Isaias (136) ; Jeremias (152) ; Baruch (170v) ; Jeremiae Lament. et Oratio (173, 174v) ; Ezechiel (175) ; Daniel (191v) ; XII Proph. min. (199).Avec prologues et « capitula » (sauf aux f. 90, 136, 152, 175, 192 et 199) . Quelques leçons en marge. F. 1-3v: Frater Ambrosius tua mihi munuscula perferens destulit...-... scripti sunt libri in latinum eos transferre sermonem. Explicit prefatio.F. 3v, tablesF. 4-124. "In principio creavit Deus caelum et terram ...-... et percutiam terram anathemate. Explicit Malachias propheta.

Delta(1232) isobar excitations in nuclear many-body systems from varios NN interactions.

Delta isobar components in the nuclear many-body wave function are investigated for the deuteron, light nuclei (16O), and infinite nuclear matter within the framework of the coupled-cluster theory. The predictions derived for various realistic models of the baryon-baryon interaction are compared to each other. These include local (V28) and nonlocal meson exchange potentials (Bonn2000) but also a model recently derived by the Salamanca group accounting for quark degrees of freedom. The characteristic differences which are obtained for the NDelta and Delta Delta correlation functions are related to the approximation made in deriving the matrix elements for the baryon-baryon interaction.

Reaction mechanisms in the (6)Li+(59)Co system

The reactions induced by the weakly bound (6)Li projectile interacting with the intermediate mass target (59)Co were investigated. Light charged particles singles and alpha-d coincidence measurements were performed at the near barrier energies E(lab) = 17.4, 21.5, 25.5 and 29.6 MeV. The main contributions of the different competing mechanisms are discussed. A statistical model analysis. Continuum-Discretized Coupled-Channels (CDCC) calculations and two-body kinematics were used as tools to provide information to disentangle the main components of these mechanisms. A significant contribution of the direct breakup was observed through the difference between the experimental sequential breakup cross section and the CDCC prediction for the non-capture breakup cross section. (C) 2009 Elsevier B.V. All rights reserved.

Indirect study of (p, alpha) and (n, alpha) reactions induced on boron isotopes

Several experiments were performed to investigate both (p, alpha) and (n, alpha) reactions induced on boron isotopes, by means of Quasi-Free (QF) reactions induced on deuteron target. The experimental study of the astrophysically relevant, (11)B(p, alpha(0))(8)Be reaction was performed by selecting the QF-contribution on the (2)H((11)B, alpha(8)(0)Be)n reaction. Moreover, due to the large interest of a better understanding of (n, alpha) reactions both for nuclear and astrophysical developments, a preliminary study of the (10)B(n, alpha)(7)Li through the QF (2)H((10)B, alpha(7)Li)p reaction was also performed. The results concerning the two experiments will be shown and discussed.

Could saturation effects be visible in a future electron-ion collider?

We expect to observe parton saturation in a future electron-ion collider. In this Letter we discuss this expectation in more detail considering two different models which are in good agreement with the existing experimental data on nuclear structure functions. In particular, we study the predictions of saturation effects in electron-ion collisions at high energies, using a generalization for nuclear targets of the b-CGC model, which describes the ep HERA quite well. We estimate the total. longitudinal and charm structure functions in the dipole picture and compare them with the predictions obtained using collinear factorization and modern sets of nuclear parton distributions. Our results show that inclusive observables are not very useful in the search for saturation effects. In the small x region they are very difficult to disentangle from the predictions of the collinear approaches. This happens mainly because of the large uncertainties in the determination of the nuclear parton distribution functions. On the other hand, our results indicate that the contribution of diffractive processes to the total cross section is about 20% at large A and small Q(2), allowing for a detailed study of diffractive observables. The study of diffractive processes becomes essential to observe parton Saturation. (C) 2008 Elsevier B.V. All rights reserved.

Um método numérico para a solução de problemas em física quântica de poucos corpos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)