J. Koperski

Study of diatomic van der Waals complexes in supersonic beams

Abstract Laser spectroscopy of van der Waals diatoms produced in supersonic beams is a source of information on the ground- and excited-state interatomic potentials. The goal of this review article is to provide a comprehensive characterization of the MeRG and Me 2 diatoms, where Me and RG are 12-group (Zn,Cd,Hg) and rare gas atoms, respectively. As a result, the ground and a number of excited states of the molecules are characterized over a broad range of internuclear separations. Analytical functions are proposed to represent the potential energy curves in three separate regions of internuclear separation: short-range region, vicinity of the equilibrium internuclear separation, and long-range limit. Several models, trends, and regularities of dispersive interaction in the studied diatoms are observed and described. The molecular characteristics presented here are compared with experimental and ab initio results of other investigators.

Interatomic potential parameters of CdHe van der Waals complex in the A30+,B31 and X10+ states – revisited

Abstract The excitation spectrum of the A0 + (5 3 P 1 )← X0 + (5 1 S 0 ) transition in the CdHe van der Waals molecule has been recorded in an experiment of a continuous supersonic molecular beam crossed with a pulsed dye laser beam. Rotational analysis of the spectrum leads to more accurate estimation of molecular bond lengths in the ground and lowest excited states. An agreement of experimental results with the most recent ab initio calculations is demonstrated.

Spectroscopical characterization of CdNe van der Waals complex in the E1(3Σ+) Rydberg state

Abstract The lowest E1 ( 3 Σ + ) Rydberg state of the CdNe van der Waals complex was investigated by an optical–optical double resonance method. The A0 + ( 3 Π) and B1 ( 3 Σ + ) states were used as intermediates in the excitation from the X0 + ( 1 Σ + ) ground state. Bound–bound excitation spectra of the E1←A0+ transition were recorded. They constitute a first observation of CdNe in the E1 state. Spectroscopical parameters of the E1-state potential well were determined. In the excitation spectrum of the E1←B1 transition, a nodal structure of bound-free transitions was observed and elucidated by a projection of the B1-state vibrational wave-function onto the E1-state potential barrier according to the prediction of ab initio calculations.

Neural networks and determination of diatomic molecule interatomic potential of cadmium dimer

A new method for obtaining a pointwise potential energy curve of diatomic molecule using Neural Network is reported. The method is employed to generate new characteristics of the B11u(51P1) electronic state of Cd2 based on LIF excitation spectrum previously recorded using the B11u←X10g+ (51S0) transition. The obtained potential provides better simulation-to-experiment agreement than those obtained using other methods. Correctness of the method is additionally tested on artificially generated LIF excitation spectra based on well characterized b30u+(53P1)←X10g+ transition in Cd2. A method for obtaining parameters of an analytical form of the potential using Neural Network applied on artificially generated Cd2 spectra is also presented.

Interatomic potentials of metal dimers: probing agreement between experiment and advanced ab initio calculations for van der Waals dimer Cd2

Abstract A critical review of experimental studies and ab initio calculations of the low-lying ungerade excited and ground state interatomic potentials of Cd2 van der Waals dimer is presented. Consistency as well as discrepancies between experimental results and ab initio calculations are probed. In order to obtain better agreement with existing experimental data, fill in gaps in current knowledge and provide a unifying framework, advanced all-electron ab initio calculations were performed and simulations of the reported spectra were executed. From simulations of laser-induced fluorescence excitation and dispersed emission spectra, analytical and/or point-wise representations of the (51P1), B11u(51P1), a31u(53P1), (53P1) and c31u(53P2) excited-, and the (51S0) ground-state Cd2 interatomic potentials were obtained. The comparison of the ab initio calculated potentials with results of the analyses allows to illustrate a current state-of-the-art of theory-and-experiment correspondence for such a demanding system. Results are presented in the context of an importance of the group 2 and group 12 metal dimer interatomic potentials especially, in ultra-cold physics and chemistry, and in fundamental tests of quantum mechanics.

Exploration of the molecular ro-vibrational energy structure: on the perspective of Yb2 and Cd2 internal cooling, and 171Yb-version of Einstein–Podolsky–Rosen experiment

ABSTRACT Schemes for internal ro-vibrational cooling in Yb2 and Cd2, as well as 171Yb Bohms spin-1/2 particle version of the Einstein‒Podolsky‒Rosen experiment based on photo-dissociation of (171Yb)2 are presented. The schemes are based on exploration of the rotational and vibrational energy structures using both theoretical and experimental approaches. GRAPHICAL ABSTRACT

Restoration of the Pure Dynamic Optogalvanic Signals in Ne Hollow Cathode Discharge

Dynamic optogalvanic signals (OGSs) from optical transitions corresponding to the Ne I 533.08-nm and Ne I 540.05-nm spectral lines are registered in Ne/Ca and Ne/Mn hollow cathode discharges. A direct deconvolution procedure has been developed for restoring the true OGS from the one registered.

Properties of the binding in 12-group homonuclear dimers from excitation and fluorescence spectra

Excitation and fluorescence ultraviolet spectra of 12-group homonuclear metal dimers (i.e., M2, where M=Zn, Cd and Hg) recorded at several molecular transitions provide information on interatomic potentials of the ground and low-lying excited electronic energy states of the dimers. In experiments the molecules were produced in a supersonic beam and were excited in a vacuum chamber using a dye-laser beam. Well-resolved vibrational structures in excitation spectra isotopic and rotational structures of the vibrational components as well as Condon internal diffraction patterns in the fluorescence bands were recorded and analyzed. Analyses of the excitation spectra lead to the analytical representations of the ground- and excited-state interatomic potentials. Analyses of the fluorescence profiles yielded information on the repulsive parts of the ground-state interatomic potentials. In the case of Cd2 and Hg2 the results confirm a relatively soft repulsion between two metal atoms in the short-range region of internuclear separation and make allowance for a theoretically predicted covalent admixture to the ground-state van der Waals binding. The hypothesis needs further corroboration. The determined interatomic potentials of mercury dimers were used in a proposed mechanism of vibrational cooling in translationally cold Hg2.

Characterization of interatomic potentials of CdRg and Zn2 molecules produced in supersonic beams

The supersonic beam method combined with techniques of laser spectroscopy has been used for determination of the excited-state interatomic potentials of the heteronuclear CdRg (Rg=rare gas: Ar and Kr) and homonuclear Zn2 van der Waals (vdW) molecules. In the experiments, the CdRg or Zn2 molecules were produced in a free-jet supersonic beam. The dimers were excited with a dye-laser beam in a vacuum chamber and the resulting total fluorescence emitted perpendicularly to the direction of the molecular and laser beams was recorded with a photomultiplier. Unstructured bound-free profiles in the CdRg that were first-time detected in the excitation at D10+(1Σ+)←X10+(1Σ+) transition as well as well-resolved bound-bound vibrational transitions in the Zn2 detected at the 30+u(3Πu)←X10+g(1Σ+g transition are presented. Analysis of the bound-free excitation spectra yielded information on the repulsive wall of the D10+-state potential in CdAr and CdKr, whereas analysis of the bound-bound excitation spectra lead to the determination of the 30+u-state potential parameters in Zn2.

Optical activity in the observation of quantum beats in forward scattered light

The technique of quantum beats in forward scattering remains a useful tool for atomic and molecular spectroscopy. The detected signal is strongly dependent on experimental conditions such as the dichroism and birefringence of external optical elements. We present a theoretical model and its experimental verification to give a physical insight into these effects.