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We present a new approach which employs a deep neural network to obtain parameters of analytical representation of potential energy curve of diatomic molecule. We test the approach to find spectroscopic characteristics for the ground X2Σ+ electronic state of MgF molecule based on the experimental energies of ro-vibrational transitions. The result shows that a deep neural network can be applied in characterisation of interatomic potential of diatomic molecule. Our approach is competitive with those obtained using other methods tested, i.e. shallow neural network and the so-called brute force method.

Spectroscopic rotational characterization of two υ

We report on the observation of a gerade Rydberg electronic energy state of Cd

Method of ro-vibrational cooling of Cd2 and Yb2 molecules occupying initially their excited ro-vibrational levels in the ground electronic state is proposed. The method employs the c31u(53P2)↔X10g+...

Spectroscopic rotational characterization of two υ ′ = 0 and υ ′ = 1 vibrational components of the E 3 Σ 1 + ( 5 s 6 s 3S1) Rydberg state of CdNe van der Waals (vdW) complex has been performed using specially designed approach. In optical–optical double resonance (OODR) process, a selective J-excitation has been realized using the E 3 Σ 1 + ← A 3 Π 0 + ( 5 s 5 p 3P1) transition, with υ ″ = 0 level of the A 3 Π 0 + state as an intermediate in the excitation from υ = 0 of the X 1 Σ 0 + ( 5 s 2 1S0) state. As a result, B υ = 0 ′ and B υ = 1 ′ rotational constants have been determined as well as the R e ′ equilibrium internuclear separation in the E 3 Σ 1 + - state potential well.

A method of experimental selection of molecular isotopologues using optical-optical double resonance (OODR) scheme and supersonic beam source of van der Waals (vdW) complexes is presented. Due to an appropriately large isotopic shift, the proper choice of a wavenumber of a sufficiently narrowband laser in the first transition of OODR scheme can lead to a selective isotopologue excitation to the intermediate state. Thanks to this approach, it is possible to select some of the isotopologues which subsequently give a contribution to laser induced fluorescence (LIF) signal originated from the final state of OODR. In this article, results of tests of the proposed method that employs the E 3 Σ 1 + ← A 3 Π 0 + ← X 1 Σ 0 + transitions in two vdW complexes, CdKr and CdAr, are presented and analysed.

Revisited study of the E3Σ1+ (63S1) ← A3Π0+(53P1) transition in CdAr using both theoretical and experimental approach is presented. Systematic detection of the E3Σ1+ in,υ' ← A3Π0+,υ″ = 6 transition frequencies with higher accuracy and spectrally narrower laser extended and improved analysis and simulation of the LIF excitation spectrum. More consistent characterization of the E3Σ1+in-Rydberg state inner well using inversed perturbation approach methodology was achieved. Free ← bound transitions in the E3Σ1+ in ← A3Π0+,υ″ = 6 excitation were taken into account in the analysis and simulation of the recorded spectrum. The updated spectroscopic characterization of the A3Π0+ state was also revisited.

Schemes for internal ro-vibrational cooling in Yb2 and Cd2, as well as 171Yb Bohm's spin-1/2 particle version of the Einstein‒Podolsky‒Rosen experiment based on photo-dissociation of (171Yb)2 are p...

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 sys...

Often, experimental spectra with only partially resolved rotational structure are observed. In such cases, determination of potential energy curves for the corresponding electronic states might be not as reliable as in the high resolution studies. In this paper, we estimate the uncertainties of the potential energy curve parameters, obtained from spectra with partially or not resolved rotational structure, where both frequencies and intensities are fitted. As an example, recently reported excitation spectrum of the B 3 1(5 3 P 1 ) ← X 1 0 + (5 1 S 0 ) electronic transition in CdAr van der Waals complex is used. Two types of Morse functions are used to model the excited state potential, but method can be readily extended to more complex potential functions. It is shown, that for reliable estimation of the uncertainties of given potential function one should take into account the possible variation of the transition dipole moment function.

A theoretical study of the relatively unexplored area of low-lying Rydberg states of van der Waals molecules (vdW) in the particular case of the CdAr system is presented. The fully ab initio calculation of the potential energy curves (PECs) of the excited vdW complex CdAr above the $(5s6s)\phantom{\rule{0.16em}{0ex}}^{\phantom{\rule{0.16em}{0ex}}3}S_{1},^{\phantom{\rule{0.16em}{0ex}}1}S_{0}$ atomic asymptotes, reaching the $(5s6p)\phantom{\rule{0.16em}{0ex}}^{\phantom{\rule{0.16em}{0ex}}3}P_{0,1,2}, (5s5d)\phantom{\rule{0.16em}{0ex}}^{\phantom{\rule{0.16em}{0ex}}1}D_{2}{,}^{3}{D}_{1,2,3}, (5s6p)\phantom{\rule{0.16em}{0ex}}^{\phantom{\rule{0.16em}{0ex}}1}P_{1}$, and $(5s7s)\phantom{\rule{0.16em}{0ex}}^{\phantom{\rule{0.16em}{0ex}}3}S_{1},^{\phantom{\rule{0.16em}{0ex}}1}S_{0}$, is performed. All the calculated PECs of the Rydberg states of $\mathrm{\ensuremath{\Sigma}}$ symmetry exhibit undulations resulting in the double-well character that was already observed experimentally in the case of the lowest Rydberg states of various 12 group metal--rare gas vdW complexes. The outer wells obtained within the present work are shallow with depths not exceeding 20 ${\mathrm{cm}}^{\ensuremath{-}1}$ below the atomic asymptote and reaching equilibrium distance of roughly 27 bohr in the case of states correlating with the $(5s7s)\phantom{\rule{0.16em}{0ex}}^{\phantom{\rule{0.16em}{0ex}}3}S_{1},^{\phantom{\rule{0.16em}{0ex}}1}S_{0}$ asymptotes. The largest calculated values of permanent electric dipoles at equilibrium distances exceed 10 D in the case of ${}^{1}\mathrm{\ensuremath{\Sigma}}$ Rydberg states correlating with $(5s6p)\phantom{\rule{0.16em}{0ex}}^{\phantom{\rule{0.16em}{0ex}}1}P_{1}$ and $(5s5d)\phantom{\rule{0.16em}{0ex}}^{\phantom{\rule{0.16em}{0ex}}1}D_{2}$ atomic asymptotes. The calculations were performed within the second-order multireference perturbation theory. The performance of this particular theoretical ab initio approach is discussed in the context of the considered type of systems and compared, wherever it was possible, with the benchmark results of the coupled-cluster method obtained in this work, with other ab initio calculations based on multireference perturbation theory and experimental data.

Expansion of Zn2 or ZnRg (Rg = rare gas atom) in a molecular supersonic beam constitutes a considerable technical challenge due to the high zinc melting point and high zinc reactivity with stainless steel at high temperatures. In order to overcome these difficulties and meet the requirements for spectroscopy of van der Waals molecules containing zinc, a high-temperature source-module of the supersonic molecular beam for aggressive elements was designed. The module was tested in the laser-induced fluorescence excitation spectroscopy experiment using the b30u+43P1←X10g+(41S0) bound ← bound transitions in Zn2. The new source-module can be used for other aggressive elements for which a laser-vaporization technique has been used to date.

Multichannel dispersed emission spectra originated upon a selective excitation of Rydberg electronic energy states in the ZnAr and CdAr van der Waals (vdW) complexes are simulated and analysed as a proof-of-concept of the future experimental approach. Simulations of the emission spectra are based on ab-initio calculated interatomic potentials and transition dipole moments (TDMs), that for ZnAr were newly calculated. Experimental set-up that is under construction along with the experimental procedure are discussed.

We report rotational profiles in the laser induced fluorescence excitation spectrum recorded for the B 3 1(5 3 P 1 ) ⿿ X 1 0 + (5 1 S 0 ) transition in CdNe van der Waals complex. A method of analyzing the rotational structure of overlapping vibrational bands with isotopic spectral contributions is discussed. Rotational characteristics B Ͽ and D Ͽ for the Ͽ⿲ = 0, 1, 2 and Ͽ⿳ = 0 are reported.

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.

Profiles of the (υ′;υ″ = 0) vibrational bands recorded using the b30+u ← X10g+ and B31 ← X10+ transitions in Cd2 and CdAr complexes, respectively, are presented and analysed. Specifically, CdAr and Cd2 complexes are simultaneously propagating in a supersonic beam. Transitions in these complexes can be used to provide the conditions for selective detection of one of the complexes in the expansion. Extended analysis of the B31- and b30+u -state vibrational progressions provided improved values for ω′ex′e and ω′e vibrational characteristics, as well as D′e well depths and Re′ bond lengths of the B31- and b30+u-state potentials. Several of the CdAr bands were recorded with partly resolved rotational structure. The new characterisation of the B31 state, along with results of the rotational and isotopic analyses of the band profiles, agrees with the most recent results of ab initio calculations, while results obtained for the b30+u state call for improvement in the ab initio calculations for Cd2.

Excitation spectra of CdNe, CdAr and CdKr complexes were recorded using the B31(53P1) ← X10+(51S0) bound ← bound and free ← bound transitions. A simulation of the dissociation continua formed by the free ← bound transitions in CdNe and CdAr permitted a determination of the repulsive part of the B31-state potential above the dissociation limit. The bound ← bound transitions in the excitation spectra of CdNe, CdAr and CdKr, and those previously recorded for CdHe and CdXe, were analyzed; by including their rotational structure and isotopic composition in the analysis, the characterization was improved. Morse functions for CdNg (Ng = noble gas) (also Lennard-Jones (12-6) for CdHe) and ab initio calculated interatomic potentials were tested for the representation of the B31-state potential above and below the dissociation limit. It was also found that previously reported ab initio calculated potentials for CdNe, CdAr, CdKr and CdXe could be modified and used. The B31-state rotational constants could be determined from the simulation of the ( υ ′ ; υ ″ ) = (2; 0)-band rotational profile in CdAr.

Analysis of profiles of ( υ ′; υ ″ = 0) vibrational bands, ( υ ′ = 0,1,2,4,5), recorded with partly resolved rotational structure using the B 3 1(5 3 P 1 ) ← X 1 0 + (5 1 S 0 ) transition in CdAr is presented. The analysis allowed for determination of the B v ′ and D v ′ rotational constants, and new values of ω e ′ vibrational frequency and D e ′ well depth of the B 3 1-state interatomic potential. The new characterization of the B 3 1 state in CdAr is closer to the result of recent ab initio calculations [Chem. Phys. Lett. 471 (2009) 29] than results of our previous study performed with vibrational resolution [Spectrochim. Acta A 56 (2000) 1613].

Comprehensive spectroscopic study of CdKr van der Waals complex in its Rydberg electronic energy state E 3 Σ 1 + ( 5 s 6 s 3 S 1 ) , using OODR process from the ground X 1 Σ 0 + ( 5 s 2 1 S 0 ) state via the intermediate A 3 0 + ( 5 s 5 p 3 P 1 ) or B 3 1 ( 5 s 5 p 3 P 1 ) states, is presented. Detection of the E 3 Σ 1 + , υ ′ ← A 3 0 + , υ ″ and E 3 Σ 1 + , υ ′ ← B 3 1 , υ ″ transition frequencies with higher accuracy and spectrally narrower laser extends previous analyses and simulations of laser induced fluorescence (LIF) excitation spectra. Potential energy curve of the E 3 Σ 1 + state exhibits double-well structure with inner (deeper) E 3 Σ 1 in + and outer (shallower) E 3 Σ 1 out + wells. More reliable characterization of both wells using inversed perturbation approach (IPA) methodology is achieved.

The method of supersonic free-jet expansion beam combined with techniques of laser spectroscopy was used in an investigation of vibronic and isotopic structures in the D 1 0 u + (6 1 S 0 ) and F 3 1 u (6 3 P 2 ) electronic energy Rydberg states of Cd 2 . Laser-induced fluorescence excitation spectra recorded using the D 1 0 u + ← X 1 0 g + (5 1 S 0 ) and F 3 1 u ← X 1 0 g + transitions in the region of 206-218 nm provided spectroscopic characteristics of the excited states and allowed constructing of their intratomic potentials. Isotopic structures recorded in the (v',v") bands of the D 1 0 u + ← X 1 0 g + transition were used in determination of the D 1 0 u + state vibrational characteristics (ω' e x' e , ω' e x' e ) and v' assignment The v 0,0 recorded directly in the F 3 1 u ← X 1 0 g + transition enabled determination of the bottom of the F 3 1 u state potential well. Valence ab initio calculations of Cd 2 interatomic potentials were performed with relativistic and spin-orbit effects taken into account. The experimental results were compared with results of the ab initio calculations. A free-jet expansion of Cd 2 as a source of entangled atoms for a test of Bell's inequality was analyzed.

Isotopic and rotational structures of the ( υ ′, υ ″) = (13,5), (14,5), (16,5) and ( υ ′, υ ″) = (0,1)–(6,1) vibrational bands of the E 3 Σ + ← A 3 Π 0 + and E 3 Σ + ← B 3 Σ 1 + transitions in CdAr, respectively, as well as the ( υ ′, υ ″) = (21,9) of the E 3 Σ + ← A 3 Π 0 + transition in CdKr were investigated using free-jet expansion beam and laser excitation. An optical–optical double resonance process was employed from the X 1 Σ 0 + + to the E 3 Σ + Rydberg via the A 3 Π 0 + or B 3 Σ 1 + intermediate electronic state. The structure of the bands with resolved isotopic structure was analyzed including their rotational structure. Analysis and simulation of the bands provided values for vibrational and rotational characteristics of the states. The analysis extended our previous low-resolution studies performed for the E 3 Σ + ← A 3 Π 0 + and E 3 Σ + ← B 3 Σ 1 + transitions.

Laser-induced fluorescence excitation and dispersed emission spectra of Cd2 recorded using the c 3 1 u ( 5 3 P 2 ) ← X 1 0 g + and b 3 0 u + ( 5 3 P 1 ) → X 1 0 g + transitions, respectively are reported. In the excitation to the c31u state, red-shaded vibrational components of several υ′ ← υ″ = 0, 1, 2, 3 progressions and Δυ = 0,1 sequences were identified. In the emission from the b 3 0 u + state, well resolved υ′ = 0,1,2,3,4 → υ″ transitions were recorded using a spectrograph with CCD camera. Analyses of the spectra provided an improved characterization of the b 3 0 u + , c31u and X 1 0 g + states involved in the transitions. The results were compared with our ab initio calculations and those obtained experimentally in earlier studies.

Laser-induced fluorescence dispersed emission spectra recorded using the C 1 Π 1 ( υ ′ ) → X 1 Σ 0 + transition in ZnKr, ZnAr and ZnNe complexes are reported. The complexes were produced in a continuous free-jet beam crossed with a pulsed dye-laser beam. The spectra were recorded using a spectrograph equipped with CCD camera. The recorded profiles displayed characteristic Condon internal diffraction patterns. The patterns consisted of reflection type continuous features corresponding to bound → free transitions and bound → bound transitions. In simulation of the spectra, M–S(9.09, 7.81), M–S(10.86, 10.32) and M–S(14.49, 8.91) Maitland–Smith M–S( n 0 , n 1 ) functions were found to represent the repulsive walls of the X 1 Σ 0 + -state potentials of ZnKr, ZnAr and ZnNe, respectively. The obtained results were compared with available experimental and theoretical representations of other studies.

Laser-induced fluorescence excitation spectra of CdRg (Rg = He, Ne, Xe) complexes were recorded at the D 1 Σ 0 + ← X 1 Σ 0 + bound ← bound and free ← bound transitions. In case of CdXe, analysis of the recorded profiles resulted in determination of the D 1 Σ 0 + -state potential energy curve and ground-state dissociation energy. In case of CdHe and CdNe, analysis of the free ← bound profiles provided a repulsive part of the D 1 Σ 0 + -state potential. Valence ab initio calculations of the ground- and excited-state potentials and electronic transition dipole moments of the studied transition were performed taking scalar-relativistic and spin-orbit effects into account. The results were supplemented with those for CdAr and CdKr of our earlier study.

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.

Laser-induced fluorescence excitation spectra observed using the D 1 Σ 0 + ← X 1 Σ 0 + transition were used to determine the D 1 Σ 0 + -state potential in ZnNe, ZnAr and ZnKr. The complexes were produced in a free-jet expansion beam and excited with a dye-laser beam from the ground to the excited state. Analysis of the unstructured free ← bound profiles yielded information on the short-range repulsive part of the D 1 Σ 0 + -state potential. Ab initio calculations of the potential energy curves for the ground and excites states as well as for electronic transition dipole moments of the studied transition were performed taking scalar relativistic and spin–orbit effects into account.

Rotational profiles of the 228Cd2 isotopomer recorded in the (υ′, υ″) = (26, 0), (27, 0), (42, 0), (45, 0), (46, 0), (48, 0) vibrational bands of the A 0 u + ← X 0 g + transition were analysed. As a result, the B υ = 26 ′ = 0.0311 ( 5 ) cm - 1 , B υ = 27 ′ = 0.0309 ( 5 ) cm - 1 , B υ = 42 ′ = 0.0279 ( 5 ) cm - 1 , B υ = 45 ′ = 0.0278 ( 5 ) cm - 1 , B υ = 46 ′ = 0.0275 ( 5 ) cm - 1 and B υ = 48 ′ = 0.0272 ( 5 ) cm - 1 excited- as well as the B υ = 0 ″ = 0.0207 ( 5 ) cm - 1 ground-state rotational constants of the (114Cd)2 were determined. The analysis allowed determining the absolute values for the R e ′ ( A 0 u + ) = 2.71 ( 7 ) A and R e ″ = 3.76 ( 4 ) A excited- and ground-state bond lengths, respectively. The obtained result – the R e ″ – distinctly shorter than that obtained with assumption of pure ground-state van der Waals bonding, supports a theoretical prediction of a covalent admixture to the bonding. Analysis of the partially-resolved rotational profile recorded in the (υ′, υ″) = (38, 0) band of the same isotopomer recorded at the B 1 u ← X 1 0 g + transition allowed estimating the B υ = 38 ′ = 0.0317 ( 2 ) cm - 1 rotational constant in the B1u state.

A method of supersonic free-jet expansion beam combined with techniques of laser spectroscopy was used in investigation of vibrational and rotational structures in the 1 0 u + ( 5 1 P 1 ) and 11u(51P1) electronic energy states of Cd2. Laser induced fluorescence (LIF) excitation and dispersed fluorescence spectra recorded at the 1 0 u + - X 1 0 g + and 1 1 u - X 1 0 g + transitions provided spectroscopic characteristics of the excited and ground states as well as a shape of the repulsive part of the ground-state potential energy curve (PEC). Rotational structures of the 228Cd2 isotopomer recorded in the (υ′,υ″) = (45,0) and (38,0) bands of the 1 0 u + ← X 1 0 g + and 1 1 u ← X 1 0 g + transitions, respectively, were used for a direct determination of the ground- and excited-state bond lengths. Moreover, the 11u-state interatomic potential was obtained numerically using an inverted perturbation approach (IPA). The position and height of the 11u-state potential barrier was determined and compared with results of ab initio calculation. Analysis of Condon-internal-diffraction (CID) profiles in the bound-free dispersed fluorescence spectrum resulted in determination of a degree of repulsion between two ground-state Cd atoms in the dimer, supporting a hypothesis of a covalent admixture to the dominant van der Waals (vdW) bonding.

Laser induced excitation and dispersed fluorescence spectra of group-12 metal homoatomic dimers (Zn2, Cd2, Hg2) recorded at a number of ultraviolet transitions provided information about interatomic potentials of the ground and lower-lying excited electron energy states of the dimers. The experimental studies were associated with calculations performed by Eugeniusz Czuchaj that were related to interatomic potentials as well as dipole moments for transitions between the ground and the excited states of the dimers. In experiments the dimers were produced in free-jet supersonic beams and were excited in a vacuum chamber with dye-laser beams. Isotopically resolved vibrational transitions in low-resolution excitation spectra and high-resolution rotational profiles of several vibrational components as well as Condon internal diffraction patterns in dispersed fluorescence spectra were recorded. Complex analyses of the spectra yielded information about the ground- and excited-state potential bond lengths, well depths as well as shapes of the investigated potentials in limited regions of internuclear separations. The determined potential energy curves were compared with results of Czuchaj providing conclusions related to the accuracy of calculations and/or experiments as well as giving the experimentalist information about planning experimental studies of molecular potentials of the group-12 dimers.

Analysis of a first-time recorded rotational structure of the υ ′ = 45 ← υ ″ = 0 band of the 1 0 u + ( 5 1 P 1 ) ← X 1 0 g + transition in 228 Cd 2 is presented. In the interpretation, an influence of a nuclear spin intensity alternation and rotational levels symmetry properties are taken into account. From the analysis, the B υ ″ = 0 = 0.0206 ± 0.0005 cm - 1 and B υ ′ = 45 = 0.0277 ± 0.0005 cm −1 rotational constants, and the R e ″ = 3.77 ± 0.04 A and R e ′ = 2.94 ± 0.03 A bond lengths are determined for the 114 Cd 114 Cd. The obtained value of R e ″ is close to that obtained with an assumption of a covalent admixture to the dominant van der Waals bonding of Cd 2 and is smaller than that derived with an assumption of pure dispersion forces.

New ab initio and revisited experimental studies of the interatomic potentials of ungerade excited and ground electronic energy states of the heavy van der Waals (vdW) dimer Hg2 were used as a “test-bed” for theory-to-experiment comparisons. Representations of the lowest excited- and ground-state Hg2 interatomic potentials were proposed, by using a new analytical approach as well as by using an inverted perturbation approach (IPA). The comparison of the new ab-initio calculated potentials with the results of the analyses illustrates an improved theory-to-experiment agreement for demanding heavy systems such as Hg2.

A new determination of the equilibrium distance Re′ out of the E3Σ+(63S1)-state potential outer well in CdAr is reported. The value was obtained taking into consideration both previously measured [Urbanczyk et al., Chem. Phys. Lett. 503 (2011) 18] excitation spectrum of the E3Σ+ ← B3Σ1+ (53P1) transition originated from υ″ = 1 as well as newly observed spectrum originating from υ″ = 2. In this study we also confirm values of ωe′ and ωe′χe′ vibrational constants of E3Σ+-state outer well.

Theoretical and experimental evidence of a weak M(z)(R) dipole transition moment between the X(1)0g+ ground and (3)1u(5(3)P1) excited states in Cd2 is presented. Two independent attempts at recording an excitation spectrum of the (3)1u elements obtained in the calculations. This work provides as a reliable starting point for further analysis of the (3)1u-state characteristics.

The lowest E1(3Sigma(+)) Rydberg state of the CdAr van der Waals (vdW) complex was investigated by means of an optical-optical double resonance (OODR) method of laser spectroscopy in conjunction with a free jet-expansion molecular beam. Two dye lasers were employed for the two-step excitation. The A0(+)(3Pi(+)) and B1(3Sigma(+)) states were used as intermediates in the excitation process from the X0(+)(1Sigma(+)) ground state. Two types of bound-bound excitation spectra of the E1

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 Me2 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.

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.

First-time observed D 1( 1 Π) v ′=10 → X 0 + ( 1 Σ) fluorescence in ZnAr, and A 0 + ( 3 Π) v ′=4 → X 0 + and D 1( 1 Π) v ′=7,8 → X 0 + fluorescence in CdAr van der Waals (vdW) molecules were produced in a continuous supersonic molecular beam crossed with a pulsed dye-laser beam, following excitation of single vibronic levels. The dispersed fluorescence spectra displayed characteristic Condon internal diffraction (CID) patterns consisting of bound–free, reflection type, continuous spectra, and, in certain cases, bound–bound discrete features. An analysis of the A 0 + → X 0 + and D 1→ X 0 + bound–bound spectra indicates that Morse functions are adequate representations of the X 0 + potential energy (PE) curves below their dissociation limits. In simulation of the A 0 + → X 0 + and D 1→ X 0 + bound–free spectra, the Morse, Lennard–Jones L–J( n −6), and Maitland–Smith M–S( n 0 , n 1 ) functions were tested, and the respective M–S(11.3, 9.0) and M–S(10.6, 7.0) potentials were found to be good representations for the repulsive walls of the X 0 + PE curves of ZnAr and CdAr, respectively, over the short range, R =2.45–4.38 A (ZnAr) and R =2.85–4.31 A (CdAr), of internuclear separations.

Excitation spectrum of Cd2 van der Waals complex was observed in a supersonic free-jet expansion beam. Cadmium dimers were seeded in argon environment (a carrier gas) while a pulsed dye laser served as an excitation light source. Well resolved structures of vibrational bands arising from transition between 1u(3pi(u)) and X0g+ (1sigmag+) states were observed. Using a Birge-Sponer method for analyzing the vibrational excitation spectrum, the first-time determination of the spectroscopical potential parameters of the 1u molecular state was performed. We obtained D'e = 723 +/- 10 cm(-1), omega'e = 28.9 +/- 1.0 cm(-1), omega'e x'e = 0.260 +/- 0.002 cm(-1) and R'e = 3.93 +/- 0.05 A. The latter value was estimated with the help of the computer-simulation of the spectrum. The results are compared with recent results of ab initio calculation of Czuchaj et al. (Chem. Phys. Lett. 225 (1994) 233) and demonstrate a reasonable agreement.

Results of new all-electron ab initio calculations and revisit of experimental studies of the interatomic potentials of lower-lying ungerade excited and ground electronic energy states of the Hg_{2} and Cd_{2} van der Waals complexes are used as probes of discrepancies between theory and experiment. From simulations of the previously and presently measured LIF excitation and dispersed emission spectra new analytical representations of the excited- and the ground-state interatomic potentials are proposed. An inverted perturbation approach was also used to improve the studied interatomic potentials. The comparison of the new ab-initio calculated potentials with the results of the analyses illustrates an improve theory-to-experiment agreement for such a demanding system like Hg_{2} or Cd_{2}.

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.

We present an analysis of the A0(+)(6(3)P(1))--X0(+)(6(1)S(0)) bound-bound and bound-free fluorescence spectrum, and of the A0(+)(6(3)P(1))--X0(+)(6(1)S(0)) and B1(6(3)P(1))--X0(+)(6(1)S(0)) bound-bound excitation spectrum of the HgKr van der Waals molecule. The A--X fluorescence spectrum, which was observed for the first time, as well as the excitation spectra were recorded using a pulsed supersonic molecular beam crossed with a pulsed dye laser beam. An analysis of the A(v')--X(v"), B(v')--X(v"), and A(v'=8)--X(v") bound-bound bands indicates that a Morse function combined with a long-range approximation represents the interatomic potential energy curve of the A, B, and X states below the dissociation limit. In the simulation of the A(v'=8)--X bound-free spectrum the Morse, Lennard-Jones (n-6), and Maitland-Smith (n(0), n(1)) functions were tested, and the Maitland-Smith (11.39, 10.50) potential was found to be a good representation of the repulsive part of the X-state PE curve above the dissociation limit, over the internuclear separation range R=2.85-3.55 Å. The spectroscopic characteristics for the A, B, and X states obtained in this work are compared with other available experimental and theoretical results. Copyright 2001 Academic Press.

B1(3sigma+)

Application of a modified version of high-temperature high-pressure all-metal pulsed source of supersonic molecular beam is demonstrated in a production of van der Waals (vdW) complexes. The vdW complexes are produced possessing controllable rotational temperature (T rot ) in the range from 3 K to 19 K. An effective control over T rot is illustrated employing excitation spectrum recorded using the B 31(53 P 1) ← X 10+(51 S 0) transition in CdAr. First-time resolved rotational structure in the profile of the υ′ = 2←υ′′ = 0 vibrational component is reported. The control over T rot is crucial in a dissociation of the (111Cd)2 isotopologue in the supersonic beam. For the process, excitation at well defined J′← J′′ rotational transition within the (υ′,υ′′) = (40,0) vibrational band of the A 10 u +(51 P 1) ← X 10 g +(51 S 0) transition is employed. It is followed by the dissociation using A 10 u +(υ′ = 40,J′′) → X 10 g + bound → free transition. An analysis and simulation of the (40,0) vibrational band rotational structure are presented. Parameters describing conditions in the supersonic beam, degree of rotational cooling, Doppler broadening and spectral bandwidth of the laser beam are used.

A 0 + ( 3 Π) → X 0 + ( 1 Σ + ) and B 1( 3 Σ + ) → X 0 + ( 1 Σ + ) fluorescence spectra of HgAr van der Waals molecules were previously produced in a pulsed supersonic molecular beam crossed with a pulsed dye-laser beam, following excitation of single vibronic levels. The dispersed fluorescence displayed characteristic Condon internal diffraction (CID) patterns consisting of bound-free reflection type, continuous spectra, and also bound-bound discrete features. An analysis of the AO+ → X0+ and B1 → XO+ bound-bound spectra indicates that a Morese function is an adequate representatation of the X0+ potential energy (PE) curve below the dissociation limit. In simulation of the AO+ → X0+ bound-free spectra of the Morse, Lennard-Jones (n − 6) and Maitland-Smith functions were tested, and the Maitland-Smith potential was found to be a good representation of the repulsive wall of the X0+ PE curve above the dissociation limit over the internuclear separation range R = 2.8–3.5 A .

An isotopically-resolved excitation spectrum recorded at the 1 0 u + (5 1 P 1 ) ← X 1 0 g + transition in Cd 2 enables to observe an influence of the nuclear spin I of atomic isotopes and rotational J -number symmetry properties on profiles and intensities of the recorded spectral components. Despite the fact that in the previously reported spectrum a rotational structure was not resolved, for its proper reconstruction it is necessary to include an analysis of the rotational structure, influence of I as well as symmetry of the molecular wavefunction in different rotational states.