Comparison with the existing experiments shows our results to be in good agreement. For state-selective cross sections, rotational coupling induces mixing between different symmetries; however, its effect, especially at low collision energies, is not as important as had been suggested in previous work. Guide to bibliographies, books, reviews and compendia of data on atomic collisions. In , the Atlanta atomic physics group published an extensive bibliography on atomic collisions. It differed from the usual in that it contained few references to individual research papers, but instead concentrated on data collections, bibliographies, review articles and books.
The present work updates the from August to September Heating rates in collisionally opaque alkali-metal atom traps: Role of secondary collisions. Grazing collisions with background gas are the major cause of trap loss and trap heating in atom traps. To first order, these effects do not depend on the trap density. In collisionally opaque trapped atom clouds, however, scattered atoms with an energy E larger than the effective trap depth Eeff, which are destined to escape from the atom cloud, will have a finite probability for a secondary collision.
This results in a contribution to the heating rate that depends on the column density of the trapped atoms , i.
For alkali-metal atom traps, secondary collisions are quite important due to the strong long-range interaction with like atoms. When extrapolating to a vanishing column density, only primary collisions with the background gas will contribute to the heating rate. This contribution is rather small, due to the weak long-range interaction of the usual background gas species in an ultrahigh-vacuum system-He, Ne, or Ar-with the trapped alkali-metal atoms.
The predictions of our model are in good agreement with the experimental data of Myatt for heating rates in high-density 87Rb- atom magnetic traps at JILA, including the effect of the rf shield and the composition of the background gas. It is shown that collisions with atoms from the Oort. Spin relaxation in ultracold collisions of molecular radicals with alkali-metal atoms. The calculations employ state-of-the-art ab initio interaction potentials and a rigorous quantum theory of atom -molecule collisions in a magnetic field based on the total angular momentum representation.
We will further discuss the relevance of the results to atom -molecule sympathetic cooling experiments in a magnetic trap.
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A quasi-classical study of energy transfer in collisions of hyperthermal H atoms with SO2 molecules. A deep understanding of energy transfer processes in molecular collisions is at central attention in physical chemistry. Particularly vibrational excitation of small molecules colliding with hot light atoms , via a metastable complex formation, has shown to be an efficient manner of enhancing reactivity. For such a study, a double many-body expansion potential energy surface previously reported for HSO 2 2 A is used.
This work was motivated by recent experiments by Ma et al. Ma et al. A 93, ]. Calculations reproduce the experimental evidence that during majority of inelastic non-reactive collision processes , there is a metastable intermediate formation HOSO or HSO 2. Nevertheless, the analysis of the trajectories shows that there are two distinct mechanisms in the T-V ET process : direct and indirect. Direct T-V processes are responsible for the high population of SO 2 with relatively low vibrational excitation energy, while indirect ones dominate the conversion from translational energy to high values of the vibrational counterpart.
Atomic vapor laser isotope separation process. A laser spectroscopy system is utilized in an atomic vapor laser isotope separation process. The system determines spectral components of an atomic vapor utilizing a laser heterodyne technique.
This dissertation discusses investigations of vibrationally and rotationally inelastic collisions of NaK with argon, helium and potassium as collision partners. Weak collisional satellite lines appear flanking strong, direct lines in the recorded spectra. Ratios of the intensity of each collisional line to the intensity of the direct line then yields information pertaining to the transfer of population in the collision.
Although it would be desirable to operate in the single collision regime, practical considerations make that difficult to achieve. Therefore, we have developed a method to estimate the effects of multiple collisions on our measured rate coefficients and have obtained approximate corrected values. Electrons and protons drive the recombination dynamics of highly excited Rydberg atoms in cold rarefied plasmas found in astrophysical conditions such as primordial recombination or star formation in H-II clouds.
It has been recognized that collisions induce both energy and angular momentum transitions in Rydberg atoms , although in different proportions, depending on the initial state, temperature and the given species considered in the collision electron or proton. Most studies focused on one collision type at a time, under the assumption that collision types are independent or their effects are not competing. The classical Monte-Carlo trajectory simulations presented in this work calculate the rates for both energy and angular momentum transfers and show their interdependence.
For example, energy transfer with small angular momentum change are more efficient for target states with initial large angular momentum. Hall, Felix H. Product branching ratios were studied using resonant-excitation mass spectrometry. For the present low-energy scattering experiments, it is shown that the energy dependence of the reaction rate constants is governed by long-range interactions in line with the classical Langevin model, but their magnitude is determined by short-range non-adiabatic and radiative couplings which only weakly depend on the asymptotic energy.
The quantum character of the collisions is predicted to manifest itself in the occurrence of narrow shape resonances at well-defined collision energies. The present results highlight both universal and system-specific phenomena in cold ion-neutral reactive collisions. Generalization of the Hartree-Fock approach to collision processes.
The conventional Hartree and Hartree-Fock approaches for bound states are generalized to treat atomic collision processes. All the single-particle orbitals, for both bound and scattering states, are determined simultaneously by requiring full self-consistency. The exact initial target and final-state asymptotic wave functions are not required and thus need not be specified a priori, as they are determined simultaneously by the SCF iterations.
To check the asymptotic behavior of the solution, the theory is applied to elastic electron-hydrogen scattering at low energies.
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The solution is found to be stable and the weak asymptotic condition is sufficient to produce the correct scattering amplitudes. The SCF potential for the target orbital shows the strong penetration by the projectile electron during the collision , but the exchange term tends to restore the original form. Potential applicabilities of this extension are discussed, including the treatment of ionization and shake-off processes.
Our results are in good agreement with recent experimental observations [L.
Ratschbacher et al. The calculated rates are 4 times smaller than is predicted by the Langevin capture theory and display a weak T The Conference was attended by participants with contributions from 54 countries. The meeting attracted contributed papers for presentation in the poster sessions. The conference included 20 Special Reports selected from the contributed papers, and these are included in part 1 of this volume. During the meeting a total of 65 Progress Reports were also presented, and the authors invited to submit written versions of their talks see Part 1.
Of the total number of contributed papers, are included as refereed abstracts in parts 2 to 15 of this volume of Journal of Physics: Conference Series. Part 1 of this volume includes detailed write-ups of the majority of plenary lectures, progress reports and special reports, constituting a comprehensive tangible record of the meeting, and is additionally published in hard-copy as the Conference Proceedings. In addition an evening public lecture by Mike Baillie on How precise tree-ring dating raises issues concerning the.
Extension of the Irregular Doublet Law
Penning ionization electron spectroscopy of CO 2 clusters in collision with metastable rare gas atoms. An unusually fast electron band with excess kinetic energies of 1. The unusual band is ascribed to autoionization into stable structures of ionic clusters to which direct ionization processes are almost impossible due to very small Franck-Condon overlaps associated with a very large geometry difference between the ionic and neutral clusters. Quantum study of Eley-Rideal reaction and collision induced desorption of hydrogen atoms on a graphite surface. H-physisorbed case.
Following previous investigation of collision induced CI processes involving hydrogen atoms chemisorbed on graphite [R. Martinazzo and G. Tantardini, J. Several adsorbate-substrate initial states of the target H atom in the physisorption well are considered, and CI processes are studied for projectile energies up to 1 eV. Results show that i Eley-Rideal cross sections at low collision energies may be larger than those found in the H-chemisorbed case but they rapidly decrease as the collision energy increases; ii product hydrogen molecules are vibrationally very excited; iii collision induced desorption cross sections rapidly increase, reaching saturation values greater than 10 A2; iv trapping of the incident atoms is found to be as efficient as the Eley-Rideal reaction at low energies and remains sizable A2 at high energies.
The latter adsorbate-induced trapping results mainly in formation of metastable hot hydrogen atoms , i. These atoms might contribute in explaining hydrogen formation on graphite. Energy-conserving, angular momentum changing collisions between protons and highly excited Rydberg hydrogen atoms are important for precise understanding of atomic recombination at the photon decoupling era and the elemental abundance after primordial nucleosynthesis.