Vladimir V. Meshkov

Direct deperturbation analysis of the AΠ2∼BΣ+2 complex of LiAr7,6 isotopomers

Direct deperturbation analysis of the highly accurate experimental rovibronic term values of the AΠ2∼BΣ+2 complex of LiAr [R. Bruhl and D. Zimmermann, J. Chem. Phys. 114, 3035 (2001)] has been performed in the framework of inverted close-coupling approach implicitly adjusted to the unified treatment of the overall A∼B coupling effect without reducing the rovibrational dimensionality. The nonlinear fitting procedure was supported by the ab initio calculations on the spin-orbit and angular coupling matrix elements between the lowest XΣ+2, AΠ2, and BΣ+2 states. The analytical grid mapping based on the reduced variable representation of the radial coordinate r was used to improve the efficiency of the solution of the close-coupling radial equations near the dissociation limit. The mutual A∼X perturbation effect on the AΠ2 term values and spin-rotation splitting of the ground state were evaluated for both LiAr7,6 isotopomers. The resulting empirical potential-energy curves for the adiabatic AΠ2 and BΣ+2 states...

Rapid, accurate calculation of the s-wave scattering length

Transformation of the conventional radial Schrödinger equation defined on the interval r ∈ [0, ∞) into an equivalent form defined on the finite domain y(r) ∈ [a, b]  allows the s-wave scattering length a(s) to be exactly expressed in terms of a logarithmic derivative of the transformed wave function φ(y) at the outer boundary point y = b, which corresponds to r = ∞. In particular, for an arbitrary interaction potential that dies off as fast as 1/r(n) for n ≥ 4, the modified wave function φ(y) obtained by using the two-parameter mapping function r(y; ̄r,β) = ̄r[1 + 1/β tan(πy/2)] has no singularities, and a(s) = ̄r[1 + 2/πβ 1/φ(1) dφ(1)/dy]. For a well bound potential with equilibrium distance r(e), the optimal mapping parameters are ̄r ≈ r(e) and β ≈ n/2 - 1. An outward integration procedure based on Johnsons log-derivative algorithm [J. Comp. Phys. 13, 445 (1973)] combined with a Richardson extrapolation procedure is shown to readily yield high precision a(s)-values both for model Lennard-Jones (2n, n) potentials and for realistic published potentials for the Xe-e(-), Cs(2)(aΣ(u)(+)(3)), and (3, 4)He(2)(XΣ(g)(+)(1)) systems. Use of this same transformed Schrödinger equation was previously shown [V. V. Meshkov et al., Phys. Rev. A 78, 052510 (2008)] to ensure the efficient calculation of all bound levels supported by a potential, including those lying extremely close to dissociation.

Diffusion in mercury-argon gas mixtures

Ab initio quantum-mechanical calculations of potential of interactions U(R) are performed for Hg-Ar. Using equations from the molecular kinetic theory of rarefied gases, a new statistical correlation is found between data on the potential of interaction (molecular beams, molecular spectroscopy, and potential U(R)) and experimental data on the mutual diffusion coefficient (MDC) of mercury-argon gas mixtures. Calculated reference data on the MDC of mercury-argon gas mixtures in the temperature range of 300 to 600 K are offered as a possible standard for calibrating instruments that measure MDCs of liquid vapors and inert gases using the Stefan method.

Ab Initio Simulation of Transport Properties in Rb–CH4 and Cs–CH4 Laser Media

The pair interaction potentials of the weakly bound Rb–CH4 and Cs–CH4 systems, which are active media of alkali metal vapor lasers with broadband diode or excimer laser pumping, were calculated by the ab initio method. The electronic problem was solved by the coupled-cluster method in the CCSD(T) version including the basis set superposition error and extrapolation to an infinite basis set. The obtained pointwise ab initio potentials were approximated by the analytical functions based on the orthogonal Chebyshev polynomial expansion with correct asymptotic behavior at the dissociation limit and then used within the framework of the molecular kinetic theory of rarefied gases to evaluate the reduced collision integrals and mutual diffusion coefficients.