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1.
Density functional approximations for systems interacting via long-range forces are revisited. The theory is illustrated with examples of one-component plasmas in two and three dimensions.Dedicated to Philippe Choquard, Coulomb fluid expert. 相似文献
2.
A model potential calculation has been applied to evaluate scattering experiments for Na and K in the groundstate and the resonance state interacting with Ar. The model potential has only two free parameters which are determined by a best fit of the interatomic potentials to experimental results. Satisfactory agreement between calculated and experimental results is found for the differential cross sections in the groundstate and the excited state, for satellites in theK(4P),K(5P) and Na(3P) line profile, for the van der Waals constantsC (6) andC (8), the alkali ion-rare gas interaction and the vibrational energy levels of the Na-Ar molecule. As maior advantages we point out that for a given pair of atoms all these calculated data are given with one single pair of values for the free parameters and that with this set also the interatomic potentials for the higher alkali states (specifically up to 5f for Na and K) are obtained. 相似文献
3.
《Surface science》1986,166(1):L141-L147
Values of the coefficients C3 and C5 which describe the asymptotic potential energy between an atom or molecule and a surface, and the constants Cs1 and Cs2 which characterize the surface mediation of the long-range atom(molecule)-atom(molecule) interaction, are calculated for rare gas and alkali or simple molecules, such as NO, H2, and H2O, adsorbed on noble and transition metals. These calculated results are obtained using analytic representations of the atomic polarizability and a numerical treatment of the substrate dielectric response obtained from measured optical constants. 相似文献
4.
The short range interactions in He2, Ne2 and Ar2 have been studied in terms of the electronic forces as functions of their internuclear separations employing their single
configuration SCF wave functions. The results show that the constituent molecular orbitals behave differently in terms of
the forces they exert on the nuclei during the interaction process. The different behaviour of the orbitals is also reflected
in the redistribution of charges. 相似文献
5.
High-level ab initio calculations are employed to generate potential energy curves for rare gas cations, RG+, interacting with neutral atoms of other rare gases, RG′, that are lighter (RG′ = Ne–Rn). The calculations employ the RCCSD(T) method, with doubly-augmented basis sets of quintuple-ζ quality. The interaction potential curves, with the full counterpoise correction applied, are calculated point-by-point. Spin-orbit coupling is applied analytically in an atom-based model. The potentials are used to calculate spectroscopic parameters, which are then compared to recent experimental work, and the very limited previous theoretical work. In addition, the potentials are used to calculate ion transport properties and the ion mobilities are compared to the few experimental data available. 相似文献
6.
K. D. Sen 《Hyperfine Interactions》1982,12(1):113-118
The radial dependence of Sternheimer quadrupole shielding-antishielding factor is reported for He, Ne, Ar and Kr atoms at the coupled Hartree-Fock level of accuracy. The results would be useful in the interpretation of the nuclear quadrupole interactions measured at the rare gas nuclei in different chemical environment such as the various van der Waals molecules. 相似文献
7.
Accurate calculations are reported of the first and second-order long-range interactions of a hydrogen atom in its ground state and a hydrogen atom in the excited 2s, 2p, 3s, 3p and 3d states. The connections with the spectroscopic states of molecular hydrogen are established. First-order mixing occurs for the n = 3 states and the form of the long-range interaction is complicated. 相似文献
8.
提出碱金属钠原子修饰笼形Si_6团簇的结构模型,采用密度泛函理论(DFT)研究钠原子修饰笼形Si_6团簇的结构及储氢性能.研究结果表明,氢分子与笼形Si_6团簇表面相互作用很弱,氢分子在其表面容易脱附.采用钠原子修饰笼形Si_6团簇后可有效避免氢分子的脱附,并且钠原子在笼形Si_6团簇的表面不发生团聚,有利于氢分子在其表面吸附和循环利用.研究发现在两个钠原子修饰笼形Si_6团簇的结构中,每个钠原子可以有效吸附六个氢分子.计算得到Na2Si_6团簇结构储氢的质量分数高达10.08 wt%,且氢分子的平均吸附能约为0.837 kcal/mol.可见,实现钠原子修饰笼形Si_6团簇结构在常温常压条件下储氢是有可能的. 相似文献
9.
Excitons in rare gas are described using the integral equation approach and an appropriate semi-empirical simplification of the short-range terms. In the solids, polarization effects are taken into account using a semi-continuum model in analogy with F-centre problem. Reasonable agreement with experiments is obtained for exciton binding energy shifts passing from atoms to crystals. 相似文献
10.
The rates of electron impact excitation of bound electronic states are calculated by interpolating the existing quantum-mechanical theories and applying an empirical correction. The calculation is done for hydrogen, helium, lithium, sodium, potassium, rubidium and cesium. The resulting rate coefficients are expressed by two parameters, the values of which are presented in tables. The error of the present calculation is estimated by comparing with available experimental data to be within a factor of approximately 2. 相似文献
11.
We present a simple, non-invasive optical technique that exploits collision-induced cross-fluorescence to monitor the amount of hydrogen in a sealed cell containing alkali metal, and reports its use in measuring the reaction rate of cesium with deuterium, both in the presence and absence of photo-excitation at 4555 Å. 相似文献
12.
F. Ancilotto E. Cheng M. W. Cole F. Toigo 《Zeitschrift für Physik B Condensed Matter》1995,98(3):323-329
Alkali atoms have been shown previously to have only unstable binding states inside liquid4He. We calculate the equilibrium configurations and binding energies of single alkali atoms near the liquid-vapor interface of4He and3He. A simple interface model is used to predict the surface deformation due to the presence of the atoms. A more realistic density functional model yields somewhat higher energies in the case of4He. For all alkali atoms, we find the surface binding energies to be around 10 to 20 K. A similar analysis with atom-H2 interactions finds that alkali atoms tend to submerge into liquid H2, with the exception of Li. 相似文献
13.
Wabnitz H de Castro AR Gürtler P Laarmann T Laasch W Schulz J Möller T 《Physical review letters》2005,94(2):023001
The interaction of intense vacuum-ultraviolet radiation from a free-electron laser with rare gas atoms is investigated. The ionization products of xenon and argon atomic beams are analyzed with time-of-flight mass spectroscopy. At 98 nm wavelength and approximately 10(13) W/cm(2) multiple charged ions up to Xe6+ (Ar4+) are detected. From the intensity dependence of multiple charged ion yields the mechanisms of multiphoton processes were derived. In the range of approximately 10(12)-10(13) W/cm(2) the ionization is attributed to sequential multiphoton processes. The production of multiple charged ions saturates at 5-30 times lower power densities than at 193 and 564 nm wavelength, respectively. 相似文献
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16.
We apply Kac's method of functional integration to a spatially non-uniform fluid with short and long-range interactions. The system with short-range interactions is treated as a reference system to which the long-range pair interaction is added as a perturbation. All equilibrium distribution functions of the reference system are assumed known. We show by diagram analysis that by a suitable choice of the density profile of the reference system the thermodynamic potential can be expressed in terms of a cluster expansion containing only irreducible diagrams. For a spatially uniform fluid in the thermodynamic limit our results reduce to those obtained by Siegert et al. 相似文献
17.
Optically pumped alkali vapor lasers are currently being developed in several laboratories. The objective is to construct high-powered lasers that also exhibit excellent beam quality. Considerable progress has been made, but there are technical challenges associated with the reactivity of the metal atoms. Rare gas atoms (Rg) excited to the np(5)(n+1)s (3)P(2) configuration are metastable and have spectral properties that are closely similar to those of the alkali metals. In principle, optically pumped lasers could be constructed using excitation of the np(5)(n+1)p←np(5)(n+1)s transitions. We have demonstrated this potential by observing gain and lasing for optically pumped Ar(*), Kr(*) and Xe(*). Three-level lasing schemes were used, with He or Ar as the collisional energy transfer agent that established the population inversion. These laser systems have the advantage of using inert reagents that are gases at room temperature. 相似文献
18.
We describe a detector for metastable rare gas atoms which allows the investigation of transverse atomic beam distributions
on the single atom level with lateral dimensions of 1 m, which occur frequently in the field of atom optics. In contrast to existing detection techniques, the conversion step from
the metastable atom to an electron is separated from the charge amplification to improve spatial resolution. The conversion
is performed at a metal surface, which is followed by an electron-optical system imaging the electron distribution with a
proper magnification onto a single electron detection unit. The spatial resolution that we achieve with this technique is
on the order of 1 m, the temporal resolution on the order of 1 s. The application of the detector for atom interferometry is discussed.
Received: 22 May 1996 / Revised version: 21 June 1996 相似文献
19.
We present a rigorous theoretical study of low-temperature collisions of polyatomic molecular radicals with (1)S(0) atoms in the presence of an external magnetic field. Accurate quantum scattering calculations based on ab initio and scaled interaction potentials show that collision-induced spin relaxation of the prototypical organic molecule CH(2)(X(3)B(1)) (methylene) and nine other triatomic radicals in cold (3)He gas occurs at a slow rate, demonstrating that cryogenic buffer-gas cooling and magnetic trapping of these molecules is feasible with current technology. Our calculations further suggest that it may be possible to create ultracold gases of polyatomic molecules by sympathetic cooling with alkaline-earth atoms in a magnetic trap. 相似文献
20.
The lower and the upper bounds for the dispersion force coefficients between hydrogen and inert gas atoms have been evaluated by using Borel integral for the dynamic multipole polarizabilities. Our evaluation for these bounds are found to be more encouraging when compared with others. 相似文献