UDC 539.19We present results of ab initio and DFT calculations of the structure and IR vibrational spectra of the monomer and dimers of N,N-dimethylformamide (DMF). The calculations were carried out in the B3LYP/cc-pVDZ approximation with subsequent force-field scaling. The calculated characteristics of the vibrational spectra of DMF show satisfactory agreement with experimental values, allowing them to be used in spectral and structural analysis.Introduction. Dimethylformamide (DMF) is one of the simplest amides and has several interesting properties. DMF does not contain an NH group, which is responsible for the nature of the intermolecular structure formed by this compound in the condensed state. The methyl and aldehyde groups act as proton donors in forming dimeric and polymeric structures of DMF. Therefore, in contrast with the closest analogs of DMF, formamide (FA) and methylformamide (MFA), the molecular clusters of DMF that are formed in the liquid phase have comparatively weak binding energies and vibrational spectra that are unperturbed by the effect of strong H-bonds. Thus, DMF is a convenient subject for studying the structural and spectral characteristics of molecular systems that are important from biological and technical viewpoints. Furthermore, liquid DMF is an important aprotic dipolar solvent. DMF often fulfills the role of an organic ligand in complexes with ions and compounds of various metals owing to the presence in it of the carbonyl.The molecular structure and vibrational spectra of DMF were studied several times both experimentally [1-9] and theoretically [7,8,[10][11][12]. However, the question of whether the molecular skeleton is planar or non-planar has not yet been answered. Also, the low symmetry of the molecule is responsible for significant interactions between vibrational modes. This causes definite difficulties in assigning vibrational bands and lines. Therefore, vibrational spectra of monomeric and dimeric forms of DMF have also not been conclusively interpreted.Herein results of quantum-chemical calculations of the structure and energy and spectral characteristics of DMF monomer and dimers are presented. Experimental IR absorption spectra are interpreted. Vibrational spectra of DMF are modeled in the gas and liquid phases.Experimental. IR absorption spectra of DMF were recorded in the range 400-4000 cm -1 on a Bruker Vertex 70 spectrophotometer. The first sample was prepared as a solution of DMF in CCl 4 (0.05 M). The second sample was pure DMF. IR spectra of the samples were recoded in a KBr cuvette (0.05 mm).Calculations. Structural and spectral characteristics of DMF monomer and dimers were calculated using the applied quantum-chemical program GAMESS [13,14]. The results were visualized using the MacMolPlt program [15]. The standard basis sets cc-pVDZ and cc-pVTZ [16], DFT methods, and the hybrid functional B3LYP [17][18][19] were utilized to optimize the equilibrium structure and calculate the force field and harmonic vibrational eigenfrequencies and intensities in IR spec...

We present CASSCF/XMCQDPT2 level of theory calculations of the ground and sixteen low-lying excited electronic states of the CsYb molecule taking into account the spin-orbit coupling. Spectroscopic constants (electronic term energies, equilibrium internuclear distances, dissociation energies, harmonic vibrational frequencies), transition dipole moments, Franck-Condon factors and vibrational energies of the CsYb molecule have been obtained. The energies of the ground and first exited states at the asymptotic limits definitely satisfy the experimental data for cesium and ytterbium atoms. All the data obtained allow to predict and realize two-photon schemes for producing ultracold CsYb molecules and carry out spectral experiments with them.

The potential energy curves of the ground and twelve low-lying excited electronic states of the RbYb molecule have been calculated using the multi-reference perturbation theory method at the CASSCF/ XMCQDPT2 level of theory including the spin-orbit coupling. The electronic term energies, equilibrium internuclear distances, dissociation energies, transition dipole moments, the sequences of vibrational energies, the harmonic vibrational frequencies, and the Franck-Condon factors have been predicted. The potential energy curves at the asymptotic limits are in a good agreement with the experimental data for rubidium and ytterbium atoms. The obtained data would be useful for spectral experiments with RbYb molecules.

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The potential energy curves of the low-lying electronic states correlating up to the limit K(4p) + Rb(5s) of KRb molecule have been calculated using the multi-reference perturbation theory method at the CASSCF/ XMCQDPT2 level of theory without and with spin-orbit coupling. The calculated parameters of the ground X 1 R + state are in the best agreement among all previously performed ab initio calculations for the KRb molecule. The calculated vibrational intervals of the ground electronic term of the 39 K 85 Rb molecule describe the experiment with the accuracy within ±1 cm À1 . The calculated intensities of the 2 1 R + (v 0 = 3, J 0 = 26) ? X 1 R + (v 00 = 0. . .24, J 00 = 25, 27) transitions satisfactory reflect the experimentally observed intensities distribution.