Andrey V. Stolyarov

Dissociative recombination of rare gas hydride ions: II. ArH +

A storage ring measurement of the rate coefficient for the production of neutral Ar in e + ArH + collisions is described. It is found that the recombination rate is too small to measure at low centre-of-mass energies but the combined rate coefficient for dissociative recombination and dissociative excitation increases above 2.5 eV displaying peaks centred at 7.5 eV, 16 and 26 eV. Calculated potential energy curves for the ground and excited states of ArH + are presented and these aid in the elucidation of the recombination and excitation processes observed at higher energies. The implications for plasma modelling are discussed.

Lifetimes and transition dipole moment functions of NaK low lying singlet states: Empirical and ab initio approach

The paper presents experimental D 1∏ state lifetime τv′J′ data and develops empirical and ab initio approaches concerning D 1∏ and B 1∏ lifetimes, as well as D 1∏–X 1∑+, B 1∏–X 1∑+ and D 1∏–A 1∑+ transition dipole moment functions μ(R) of the NaK molecule. Experimental D 1∏(v′,J′) state τv′J′ values for v′ varying from 1 to 22 have been obtained from experimentally measured electric radio frequency-optical double resonance (rf-ODR) signal contours. The rf-ODR signals have been produced by D 1∏←X 1∑+ laser induced optical transition and rf field (1–900 MHz) induced e–f transition within the D 1∏(v′,J′) level. The possibility to determine empirical absolute μ(R) function in a wide R range from experimental τv′J′ dependence on v′ and J′ has been demonstrated; such an approach has been applied to obtain μ(R) for the B 1∏–X 1∑+ transition on which relative intensity data are absent. The empirical D 1∏–X 1∑+μ(R) function has been considerably improved by simultaneous fitting of relative intensity and lifetime d...

The phase formalism for the one-dimensional eigenvalue problem and its relation with the quantum Bohr-Sommerfeld rule

A quantum phase formalism is offered for searching for eigenvalues of the one-dimensional Schrodinger equation. Its application in the shooting method appreciably sped up convergence and made it absolute. The introduced quantum phase functions are close to their semiclassical analogues, unlike those used before, and transform into them in the semiclassical limit. A form of quantum analogue of the Bohr-Sommerfeld quantisation rule, allowing it to operate with non-integer quantum numbers within the framework of precise quantum consideration is obtained.

The X2Σ+ state of LiCa studied by Fourier-transform spectroscopy

The paper reports on a successful observation of high resolution Fourier transform spectra of LiCa. The fine structure of the ground state was observed and attributed to effective spin-rotation interaction. The experimental observations are described by two models using potential energy curves. One of them takes into account the fine structure splitting by means of effective constants, the other by means of a R dependent function γ(R), built in the radial Schrödinger equation. Ab initio calculations were performed for γ(R) which comes close to the experimental function.

Identification of Deeply Bound Heteronuclear Molecules Using Pulsed Laser Depletion Spectroscopy

We demonstrate that a near-dissociation photoassociation resonance can be used to create a deeply bound molecular sample of ultracold NaCs. To probe the resulting vibrational distribution of the sample, we use a new technique that can be applied to any ultracold molecular system. We utilize a tunable pulsed dye laser to produce efficient spectroscopic scans (∼ 700 cm at a time) in which we observe the 1Σ → 2Σ − 2Π vibrational progression, as well as the dissociation limit to the Cs 62P3/2 asymptote. We assign 1 Σ(v = 4, 5, 6, 11, 19) vibrational levels in our sample.

APPROXIMATE SUM RULE FOR DIATOMIC VIBRONIC STATES AS A TOOL FOR THE EVALUATION OF MOLECULAR PROPERTIES

Abstract The approximate sum rule ≈ Σv2 (Ev1 - Ev2)n, where f, g are operators which couple the vibrational levels v1, v2 of two interacting electronic states and ΔU=U1—U2 is the difference of the corresponding internuclear potentials, is numerically tested for radiative lifetimes, electronic polarizabilities, fine-structure constants and Lande factors for the vibronic states of the NaK molecule. The approximation is demonstrated to have high accuracy and efficiency for non-diagonal systems, especially for those with significant continuum contributions. Simple ways of estimating the sum rule accuracy are given.

The I-2(B) predissociation by solving an inverse atoms-in-molecule problem

The valence electronic states of the iodine molecule are analysed by means of a simple atoms-in-molecule model which accounts for the lowest 2P states of iodine atoms and approximates the spin-orbit interaction by its atomic part. For this model, an inverse problem is solved, i.e. non-relativistic potential energy curves and diabatic couplings are determined by a least-squares fit to known relativistic potential energy curves. The resulting adiabatic wave functions are used to calculate the electronic matrix elements responsible for natural, hyperfine and magnetic predissociation of the iodine molecule in the B0+ u: state. The results are in reasonable agreement with experimental data, being stable enough with respect to the variation of input relativistic potentials. They also indicate the importance of diabatic couplings between the non-relativistic states of the same symmetry.

Radiative properties of diatomic Rydberg states in quantum defect theory. Application to the hydrogen molecule

Single-channel quantum defect theory (QDT) is used to approximate the Born-Oppenheimer electronic wavefunction of Rydberg diatomic states. The development is based on an extension of quantum-mechanical and semiclassical approaches for the estimation of molecular transition dipole matrix elements as a function of internuclear distance R . The theory is tested by a calculation of the singlet and triplet transition moments of the molecule involving Rydberg states with n = 2-4; l = 0-2. For small and moderate internuclear distance the agreement with ab initio data is found to be generally good, and in some cases identical results are obtained. The disagreement is attributed to a breakdown of the one-channel QDT representation of the interacting electronic states for large R values. The predicted moments for - and - transitions remove existing discrepancies between theoretical and accurate experimental lifetimes for and states.

Alignment‐orientation conversion by quadratic Zeeman effect: Analysis and observation for Te2

This paper reports the observation of the molecular fluorescence circularity under irradiation with linear polarized light. The phenomenon arises as a result of partial transformation from alignment of the ensemble of molecular angular momenta into orientation due to quadratic correction to Zeeman effect. Circularity rate up to 0.05 at magnetic field 0.4 T was registered in B 3Σu−(1u−)→X 3Σg−(1g−) fluorescence of 130Te2 molecules at angle π/4 with respect to E vector of linear polarized exciting light. Quadratic magnetic energy terms are associated with magnetic field induced ΔJ=±1 e/f mixing between 1u−∼1u+ and 1u−∼0u+ states. Circularity data fitting shows that the electronic part of Lande factor caused by 1u−∼0u+ interaction is equal to G± ≂gl〈0u‖Ja±‖1u〉+(gs−gl) 〈0u‖S±‖1u〉≂2.72.

Potential Energy Curves for Alkali Metal - Rare Gas Exciplex Lasers

Lasers driven by optical pumping of alkali metal rare gas collision pairs have been demonstrated recently. Accurate potential energy curves for the alkali metal rare gas dimers are need to analyze and predict the scaling characteristics of this type of laser system. We are using high-level theoretical methods to obtain these data and predict the absorption spectra. The potential energy curves, transition dipole moments, and spin-orbit coupling matrix elements for MRg (M=Rb,Cs and Rg=Ar,Kr) electronic states converging to the lowest three dissociation limits have been characterized. Quasi-relativistic matrix elements have been obtained for a wide range of internuclear distances using different sets of small core relativistic pseudopotentials. The core-valence correlation was included in a large-scale multi-reference configuration interaction (MR-CI) treatment. Excited state potentials were also examined using multi-reference averaged quadratic coupled cluster (MR-AQCC) methods. The data obtained from these calculations have been used to predict the absorption spectra for the MRg pairs using semi-classical and quantum mechanical models.