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[en] The specific anisotropic interactions between HD molecules stemming from the fact that the HD molecules rotate not around their geometric centers can account for the structure anomalies found in experiment. At comparatively moderate pressures (below 10 kbar) the specific anisotropic interactions compare with the electrical quadrupole-quadrupole interaction and can be the decisive factor in forming the eventual orientational order parameter to appear in a pressuredriven phase transition
[en] We have studied the resonant two-photon dissociation (TPD) of vibrationally excited HD+ by both 1sσ/sub g/→1sσ/sub g/ vibrational and 1sσ/sub g/→2pσ/sub u/ electronic transitions. Following Armstrong et al., a quantum mechanical description of the laser field enabled us to define the intermediate resonant state as a ''pseudodissociating state'' of the molecule--radiation system. This makes our theory formally similar to that of single-transition (photon) autoionization problem as formulated by Fano. This similarity has been exploited to obtain the intensity dependent line shapes of the resonant TPD of HD+. Resonant TPD cross sections from the v/sub i/ = 6, J/sub i/ = 0 level of the ground 1sσ/sub g/ state of HD+ are calculated with a linearly polarized infrared laser radiation in the wavelength range 16 530--16 565 A and at different intensities ranging from 1.53 x 108--3.83 x 1013 W/cm2. Effects of laser intensity on the linewidth, line shift, and cross sections are found to be very different for the two types of transitions. Our previous results of nonresonant TPD cross sections are reproduced via this model
[en] A detailed theoretical analysis of the intensities of the pure rotational R0(J) transitions in gaseous HD is presented. These transitions all manifest small intracollisional interference effects arising from the cross product of the allowed-- and the induced--dipole-moment matrix elements. Using recent ab initio calculations of the induced dipole moment in an HD-HD pair, this interference is found to be constructive for most transitions, thus implying a density-dependent increase in intensity. For the R0(0) transition, a small but significant additional contribution to the constructive intracollisional interference results from the mixing of rotational levels in a single molecule during collisions. Additionally, because of a near-resonance condition, simultaneous mixing of internal rotational levels in both molecules of a colliding pair leads to a large destructive interference affecting primarily the R0(2) transition. The present theoretical values of the interference parameter a/sub theor/ are compared with experimental data and it is concluded that while the low-temperature data are in reasonable accord with the present theoretical results, significant differences still remain both between different experimental determinations, and between theory and experiment for the room-temperature data. Possible theoretical refinements to explain the observed large temperature dependence of the intracollisional interference are discussed briefly
[en] Sub-Doppler excitation spectra of HD have been recorded in the range 92--98 nm with the use of a narrow-band and tunable extreme ultraviolet laser in combination with a molecular beam. Frequencies of 147 transitions to the B 1Σu+, C 1Πu, and EF 1Σg+ states have been calibrated with an average absolute accuracy of 0.035 cm-1. The data have been analyzed in the framework of a semiempirical deperturbation model involving mutual couplings between nearby lying levels of the B 1Σu+ and C 1Πu states. Also, symmetry-breaking effects, i.e., interactions with EF 1Σg+ gerade states, were inferred from the data
[en] To develop a real time and in-situ process gas analyzer for fusion fuel gas processing systems, application study of laser Raman spectroscopy was performed by measurement of hydrogen isotopes. Using an Ar ion type laser of which wavelength 488 nm, power 0.7 W, and single pass irradiation method, Raman spectra of hydrogen isotopes were measured and intensities of the Stokes rotational lines and Q-branch were quantitatively analyzed. The Stokes rotational lines at 587, 443 and 415 cm-1 were selected as suitable ones for quantitative analysis of H2, HD and D2. Normalizing the Raman intensity of partial pressure H2 as 100, relative Raman intensity ratio of H2 : HD : D2 was obtained as 100 : 58 : 47. The detection limit for hydrogen was estimated as 0.05 kPa in partial pressure and 500 ppm in concentration. But multiple pass method further improved the detection limit to 100 ppm. (author)
[en] We use high-resolution three-dimensional adaptive mesh refinement simulations to investigate the interaction of high-redshift galaxy outflows with low-mass virialized clouds of primordial composition. While atomic cooling allows star formation in objects with virial temperatures above 104 K, 'minihalos' below this threshold are generally unable to form stars by themselves. However, these objects are highly susceptible to triggered star formation, induced by outflows from neighboring high-redshift starburst galaxies. Here, we conduct a study of these interactions, focusing on cooling through non-equilibrium molecular hydrogen (H2) and hydrogen deuteride (HD) formation. Tracking the non-equilibrium chemistry and cooling of 14 species and including the presence of a dissociating background, we show that shock interactions can transform minihalos into extremely compact clusters of coeval stars. Furthermore, these clusters are all less than ∼106 M sun, and they are ejected from their parent dark matter halos: properties that are remarkably similar to those of the old population of globular clusters.
[en] Van-der-Waals cluster formation of the hydrogen isotopologues in the windowless gaseous tritium source (WGTS) of the Karlsruhe Tritium Neutrino Experiment (KATRIN) influences the measured electron energy spectrum. Therefore it represents a systematic uncertainty for the neutrino mass measurement with KATRIN. In the cryogenic distillation column of the fusion fuel cycle, this cluster formation also limits the accuracy of the measurement of the concentration of liquid hydrogen isotopologues based on infrared (IR) absorption spectroscopy. This thesis presents the investigation of this cluster formation via IR absorption spectroscopy. In this thesis, a description of the band structure of the IR absorption spectra of the Van-der-Waals clusters of inactive hydrogen isotopologues is developed and the major contributions to the line shapes are determined. Based on this, the temperature dependency of the absorbance of the Van-der-Waals clusters is experimentally determined in the liquid and gaseous phase and conclusions towards the cluster formation are drawn.
[en] Spectroscopic observation of the highest vibrational level of HD+(v = 21) in its ground electronic state is reported. Calculations of constants from the resolved hyperfine structure allow unambiguous determination of the Fermi contact parameters for the levels 17,1 and 21,0, showing that in the level 21,0 the electron distribution is asymmetric toward the lower dissociation limit H++D, with an average electron density of 0.094 at the proton and 0.902 at the deuteron
[en] In the study of wake effect resulting from the reaction of HD2+ with thin carbon foil, we find one striking use of wake effect is that it can be applied to determine the structure of micro-cluster ions which cannot be detected use normal Coulomb Explosion technique only. In this paper, we report this method of determining the triatomic molecular HD2+ by using the new theoretical model of wake effect for triatomic molecular we proposed. The basic idea of this method is that the pattern of the coulomb explosion spectrum is very sensitive to the nuclei separation of micro-cluster. (authors)
[en] The R(0) and R(1) line shapes of HD are of interest because observation of these lines in the atmosphere of the outer planets should lead to unambiguous values of the D/H ratio. The electronic potential energy surfaces used to calculate HD--He and HD--H2 line shape cross sections have been well validated in previous publications of this series. The results of two additional tests of the electronic potential energy surface of hydrogen-like systems are reported here: the second virial coefficient of para-hydrogen at low temperatures and HD--D2 elastic and inelastic differential scattering cross sections. Formulas are given for Dicke narrowing as well as for the line broadening and shift cross sections calculated here. Close coupling calculations were carried out for the R(0) and R(1) transitions of HD immersed in He and for the R(0) transition of HD immersed in H2. These cross sections are anticipated to be quite reliable at temperatures above 50 K, i.e., where clustering can be ignored