Marcin Gronowski

Computational Chemistry

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Posts Tagged ‘rotational spectroscopy’

Ab Initio Studies of the Structure and Spectroscopy of CHNMg Stoichiometry Molecules and van der Waals Complexes

A high-level ab initio study was conducted over the range of tetraatomic molecules containing H, C, N, and Mg. Potential energy surfaces were analyzed, leading, for selected molecules, to the optimization of their geometry in the lowest singlet and triplet excited states. Reliable ground state rotational constants are given for the most stable species, namely, HMgNC and HMgCN, together with respective anharmonic vibrational frequencies of fundamental, overtone, and combination bands. In addition, potential energy surfaces describing the interaction of HCN or HNC with a single magnesium atom have been investigated.

Full text: J. Phys. Chem. A, 2013, 117 (21), pp 4455–4461

PROSPECTS FOR THE DETECTION OF INTERSTELLAR CYANOVINYLIDENE

Prospects for the presence and detection of interstellar cyanovinylidene, CC(H)CN, a Y-shaped isomer of cyanoacetylene, are discussed. It is proposed that CC(H)CN can arise in interstellar clouds as one of the HC3NH+ + e– dissociative recombination products, by rearrangements of the neutral chain radical HC3NH into branched species HCCC(H)N, CC(H)C(H)N, and/or HCC(H)CN, and by the subsequent elimination of a hydrogen atom. It is deduced that the abundance of cyanovinylidene in molecular clouds should be confined between the abundances of its chain isomers HNCCC and HCNCC. Quantum chemical predictions regarding cyanovinylidene geometry, ground-state rotational constants, centrifugal distortion constants, spin-orbit coupling, IR absorption spectroscopy, and electric dipole moment are given. The spectroscopically observed molecules formyl cyanide, NC2(H)O, and propynal, HC3(H)O, with structures qualitatively resembling cyanovinylidene, served to prove the adequacy of the calculational procedures employed.
Full text: Astrophys. J. 701 (2009) 488

Isomers of cyanodiacetylene: Predictions for the rotational, infrared and Raman spectroscopy

Recent ab initio (coupled-clusters) and density functional theory studies on cyanodiacetylene isomers are extended here to yield the quantities of direct interest to future spectroscopic investigations. A bond lengths scaling procedure was developed to obtain the corrected molecular geometries. These, together with calculated vibration–rotation coupling constants, yielded the ground-level rotational constants for seven most stable isomeric species of the HC5N stoichiometry. Former calculations regarding the vibrational transitions of these molecules are complemented here with predictions on Raman scattering activities, and on isotopic (2H, 15N) effects in IR absorption and Raman spectra.
Full text: J. Mol. Struct. 834-836 (2007) 102