Calculation of the spectroscopic parameters of van der waals diatomic molecules: An excited alkali Na or K atom and an inert gas atom

The interatomic potentials in a system of an excited Na or K atom and an inert gas atom are calculated on the basis of the effective pseudopotential method, using a new form of the polarization interaction potential obtained by calculating the most important polarization diagrams of perturbation theory in the Thomas-Fermi approximation. The results of a calculation, on its basis, of the intermolecular terms of this van der Waals system are given, refining the existing data; some of the results have been obtained for the first time. A comparison is made with the available experimental and theoretical data. Odessa Hydrometeorological Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 32–35, September, 1996.     

Calculation of spectroscopic parameters of diatomic van der waals molecules and ions: inert-gas atom-inert gas ion of the halogen-type in the ground state

Based on the effective-pneudopotential method with the use of a new form of the polarization-interaction potential, obtained on the basis of calculating the most important polarization diagrams of the perturbation theory in the Thomas—Fermi approximation, the authors calculated interatomic potentials in the inert-gas ion in the ground state-inert-gas atom system: Ne⁺, Kr⁺−Ne, Ar, Kr, Xe. The results of calculating on its basis quasi-molecular terms of the sought van der Waals systems that refine the available data are given; a part of the results is obtained for the first time. Odessa Hydrometeorological Institute, 15, L’vovskaya St., Odessa, 270016, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 935–938, November–December, 1998.     

Calculation of spectroscopic parameters of diatomic van der walls molecules: Inert gas atom-halogen atom

Based on the effective pseudopotential method with the use of a new form of the polarization interaction potential that is obtained from calculating the major polarization diagrams of perturbation theory in the Thomas-Fermi approximation a calculation of interatomic potentials in the “halogen atom in the ground state F—inert gas atom Br” system is performed. The results of calculating on its basis the quasimolecular terms of the sought van der Waals system that ascertain the available data are given. Comparison with the available experimental and theoretical data is made. Odessa Hydrometeorological Institute, 15, L'vovskaya St., Odessa, 270016. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 256–259, March–April, 1997.     

Calculation of diatomic van der Waals systems inert gas atom-halogen type inert gas ion in the ground state

Interatomic potentials are calculated for the systems inert gas ion in the ground state-inert gas atom Ne⁺, Xe⁺-Ne, Ar, Kr, Xe, Fr. The calculation is performed by the effective pseudopotential method using the new form of the polarization interaction potential obtained by calculating the most important polarization diagrams of perturbation theory in the Thomas-Fermi approximation. The quasimolecular states of these van der Waals systems are calculated to refine the available data; some data are obtained for the first time. Translated from ZhurnalStrukturnoi Khimii, Vol. 39, No. 4, pp. 591–595, July–August, 1998     

Calculation of the spectroscopic characteristics of biatomic van der Waals molecules and ions: Inert gas atom — halogen-type inert gas ion in the ground state

The interatomic potentials in a system formed by an ion of an inert gas in the ground state and an atom of an inert gas (e.g., Ne⁺, Ar⁺-Ne, Ar, Kr, Xe) are calculated on the basis of a calculation of the most important polarization diagrams of perturbation theory in the Thomas-Fermi approximation. The calculation employs the effective pseudopotential method using a new form of the polarization interaction potential. Results are presented from a calculation of the quasimolecular terms of particular van der Waals systems that improve existing data; some of the data were obtained in earlier studies. Odessa Hydrometeorological Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 36–40, March, 1998.     

Comparison of the ground state vibrational fundamentals of diatomic molecules in the gas phase and in inert solid matrices

Despite the voluminous literature on the spectra of diatomic molecules, there are many gaps in our knowledge of their ground state vibrational frequencies. For many important diatomic molecules, only values obtained in matrix isolation experiments are available. In order to assess the likely extent of deviation of the ground state $\text{ΔG(}\text{1}\text{2}\text{)}$ values of diatomic molecules observed in rare-gas and nitrogen matrices from the gas-phase values, a systematic comparison has been made between gas-phase and matrix frequencies. The dependence of matrix shifts on the matrix material and type of chemical bond is considered for the approximately 230 pairs of observations, spanning the entire Periodic Table, which have been reported. Except for van der Waals molecules and for the Group Ia and IIIa halides, the argon-matrix shift for most diatomic molecules is less than 2%.     

Nonlinear dipole-dipole interactions and spectroscopic properties of van der waals complexes in the gas phase

We suggest a semiempirical approach to describing the influence of local nonlinear dipole-dipole interactions on the formation of van der Waals complexes of 1: 1 composition in the gas phase. Based on this approach, we quantitatively interpret the experimental data on the patterns of the shift in the electronic (complexes of a 3-aminophthalimide molecule with water and methanol molecules) and vibrational (complexes of a HCl molecule with acetone and acetonitrile molecules) absorption spectra attributable to the processes of complex formation. We confirm the conclusion that a nonlinear dipole-dipole interaction should be considered as one of the most important physical mechanisms that result in the association of molecules both in the gas phase and, under certain conditions, in the condensed state.     

Ab initio determination of spectroscopic parameters for ethane-like molecules in the ground vibrational state

The quadratic rotational constants A and B and torsional barrier V₃, distortion parameters D_J, D_K, and D_JK, torsional distortion parameters D_m, D_Jm, and D_Km, and barrier-dependence parameters F_3J, F_3K, and F_3m have been determined for CH₃CH₃, CH₃CD₃, CD₃CD₃, and CH₃SiH₃ from the results of ab initio calculations done at the CCSD(T) level. Calculated values for the first six parameters are consistently within about 1% of experimental values, while the relative errors for D_m, D_Km, F_3J, and F_3K are generally less than 20%. Calculation of the parameters D_Jm and D_sJ is found to be more problematic, even with the application of vibrational averaging in the harmonic oscillator approximation. There is evidence that this is due to the influence of vibrational contact transformations in the experimental values.     

Accurate relations for the isotopically invariant spectroscopic parameters of diatomic molecules

Equations are obtained relating the isotopically invariant spectroscopic parameters U_mj, which must be considered as conditions in the least-squares method in spectral analysis. Expressions are given for the first seven Dankhem potential parameters in terms of U_m0 and U_m1. The contribution to the spectroscopic coefficients Y_mj due to violation of the Born-Oppenheimer approximation is calculated for¹²C¹⁶O.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 18–21, November, 1984.It remains to thank Yu. S. Makushkin, V. Ya. Galin, andV. F. Golovko for valuable discussions of the work.     

Mechanical effect of van der waals interactions observed in real time in an ultracold Rydberg gas

We present time-resolved spectroscopic measurements of Rydberg-Rydberg interactions between two Rydberg atoms in an ultracold gas, revealing the pair dynamics induced by long-range van der Waals interactions between the atoms. By detuning the excitation laser, a specific pair distribution is prepared. Penning ionization on a microsecond time scale serves as a probe for the pair dynamics under the influence of the attractive long-range forces. Comparison with a Monte Carlo model not only explains all spectroscopic features but also gives quantitative information about the interaction potentials. The results imply that the interaction-induced ionization rate can be influenced by the excitation laser. Surprisingly, interaction-induced ionization is also observed for Rydberg states with purely repulsive interactions.     

Calculation of a one dimensional van der waals liquid-gas transition by means of a Ginzburg-Landau expansion

The grand canonical partition function written as a Feynman path integral over the order parameter is calculated numerically within the framework of a Ginzburg-Landau theory for a one dimensional van der Waals system. The equation of state is calculated. The results show that the transition is of quasi first order.     

Shift of the magnetic resonance frequency in a system consisting of a metastable helium atom and a potassium atom in the ground state

The shifts of the magnetic resonance frequency in a system comprising a metastable helium atom and a potassium atom in the ground state are calculated. It is shown that the shift cross section decreases as the temperature grows from 50 to 400 K, remaining negative throughout the temperature range.     

Spectroscopic manifestations of isotope substitution in ultrasound jet-cooled complex molecules and their van der waals complexes

It is shown that, upon formation of ultrasound jet-cooled var der Waals complexes of polar molecules of 9-cyanoanthracene, 3-aminophthalimide, and 3-amino-N-methylphthalimide with water molecules, pronounced manifestations of isotope substitution in the ligand molecules take place, which manifest themselves in shifting 0–0-transitions by 5–7 cm⁻¹ and changes in frequencies of intramolecular vibrations. Spectroscopic effects of isotope substitution of atoms of the amino group are established for substituted phthalimides. We propose a new mechanism of the effect of isotope substitution on frequencies of electronic transitions which cannot be reduced to the known one (realized by means of changes in values of the zero vibrational energy) and is based instead on the change in the charge density distribution in the molecule. Belarusian State University, 4, F. Skorina Ave., Minsk 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 148–154, March–April, 1997.     

Estimate of P-and P,T-odd effects in diatomic van der Waals molecules

The magnitudes of the possible P-and P, T-odd effects in diatomic van der Waals molecules are estimated. The estimates fall between the values corresponding to atoms and molecules/radicals. Arguments are presented showing that the loss of approximately two orders of magnitude in the strength of the effect for van der Waals molecules with an unpaired electron, such as CsXe, as compared with molecules/radicals can be partially compensated by a number of experimental advantages of working with van der Waals molecules. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 10, 659–663 (25 November 1996)     

Calculation and use of the coefficients in Dunham's function to determine the spectroscopic characteristics of diatomic molecules

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 52, pp. 451–454, March, 1990.     

Inversion-rotation spectrum and spectroscopic parameters of 14ND3 in the ground state

The far-infrared spectrum of ¹⁴ND₃ has been recorded in the region between 30 and 220 cm^?1 at a resolution, before deconvolution, of approximately 0.004 cm^?1. ΔJ = +1, ΔK = 0, a ← s and s ← a inversion-rotation transitions have been measured and assigned up to J″ = 19. These transitions, the pure inversion-microwave transitions and ground-state combination differences from the analysis of the ν₂ and ν₄ bands have been fitted simultaneously to an inversion-rotational Hamiltonian which includes Δk = ±3 and Δk = ±6 interaction terms. The ground-state spectroscopic parameters obtained in this way reproduce the transition frequencies within the accuracy of the measurements.