Calculations of V−V Transfer Rates in H₂ and Comparison with Experiment

Abstract

Recent observations on VV transfer in H(2) have shown interesting results. For nonresonant processes, comparison of the experimental rate constants with the results of previous semiclassical calculations, quantum oscillators/classical rotors coupled via classical collisions, showed the theoretical rate constants to be too slow by a factor of 3 or more. The semiclassical rate constant of the resonant VV process (v = 1 + v = 0 --> v = 0 + v = 1) was also found to be too slow, by more than an order of magnitude, compared with the experimental rate. Further, the semiclassical model predicted the value of k(1,1-->0,2) to exceed that of k(1,0-->0,1), but the experimental data shows it to be a factor of approximately 2 less. In this work we employ an accurate interaction potential for the H(2)-H(2) system, and treat both rotation and vibration of the diatoms as coupled quantum-mechanical degrees of freedom. These new calculated results are in better overall agreement with the near-resonant experimental values, but the calculated rate constants are a factor of 2 to 3 larger than experiment for the nonresonant processes.

Thermal Ring‐Opening of Pyrazolo[3,4‐d][1,2,3]triazin‐4‐ones: An Experimental and Theoretical Study

“…[1] In particular, azole-annulated 1,2,3-triazines possess activity as anti-virals and anti-tubercular agents, inhibitors of protoporphyrinogen oxidase, herbicides, and pesticides, among others. [2][3][4] In view of the important biological activities of purine analogues, our research interests have been focused on the synthesis of pyrazolo [3,4-d][1,2,3]triazin-4-ones and imidazo [4,5-d][1,2,3]triazin-4-ones, establishing a convenient method to access a broad range of these derivatives through the one-pot diazotization of 5-aminoazole-4-carbonitrile precursors. [5,6] We found that the stability and transformations of the diazonium ion intermediate was strongly dependent on the type of azole ring and, to a lesser extent, the nature of the substituent at N-1.…”

“…[5,6] We found that the stability and transformations of the diazonium ion intermediate was strongly dependent on the type of azole ring and, to a lesser extent, the nature of the substituent at N-1. [6] Concerning the chemical reactivity of azole-annulated 1,2,3triazinones, it has been found that modifications at the carbonyl group lead to 4-substituted azolo-triazines, [2,4,7] alkylation at N-3 [8] and opening of the triazine ring with elimination of nitrogen afford pyrazole derivatives [9][10][11][12] or pyrazolyl-pyrazolooxazinones by the dimerization of an iminoketene intermedi-pyrazolotriazinones involves the generation of an iminoketene intermediate, which reacts with a second molecule of pyrazolotriazinone. The complete mechanism of product formation involving the iminoketene intermediate, and all other reasonable pathways, have been explored in detail through DFT calculations.…”

Many-body theory of surface-enhanced Raman scattering

“…In this way, deficiencies in the theory are corrected, leading to predictions which compare sensibly with experiment [22,24,25]. Two additional notable quantum approaches to SERS based upon density-matrix calculations have recently appeared in the literature [26,27]. The interaction of a Raman-active molecule supporting two electronic states (plus several vibrational substates) with two nearby nanoscale Ag spheres, described through an extended Mie theory, is presented in Ref.…”

“…Second, in Ref. [27], enhanced resonance Raman phenomena are studied within a combined eight-state density-matrix approach where the molecular subsystem is represented in a four-state basis involving molecular ground and electronic, vibrational, and electronic and vibrational excited states while the particle subsystem is represented in a two-state basis consisting of ground and excited states. Within this model, it is predicted that the largest resonance Raman enhancements occur when a molecule, which absorbs light far from the particle's resonance maximum, is excited at the resonance maximum of the particle.…”