Large scale vibrational Hamiltonian calculations on thiophosgene

A combined theoretical treatment of T1→S intersystem crossing and intramolecular vibrational redistribution in thiophosgene

“…,n 6 ͘Љ in terms of symmetrized curvilinear vibrational coordinates ͕Q k ͖, has been defined in our recent work. 7 In that work, large scale vibrational Hamiltonian calculations have been performed on the vibrational frequencies and the potential energy surface of ground electronic state thiophosgene, including all six vibrational modes. From a good fit achieved between the theoretically calculated and an extensive set of experimentally measured and assigned vibrational frequencies by Strickler and Gruebele, 8 the harmonic and some anharmonic ͑cubic and quartic͒ force constants of the molecular potential energy surface have been determined.…”

A refined quartic potential energy surface and large scale vibrational calculations for S0 thiophosgene

“…Several model 6D potential fields for S 0 thiophosgene have been calculated so far in the literature [4,21,22]. The ab initio field of Strickler and Gruebele [4] has been calculated with bond distance coordinates and then refined using over 100 vibrational levels up to $8000 cm À1 .…”

“…For their vibrational calculations, Davisson et al [22] used the so called VPT2+K approach, which is based on second order vibrational perturbation theory with resonances treated explicitly using a Hamiltonian formalism. Our earlier empirical field [21], was of limited scope and applicability since our vibrational calculation method involved a simplified (approximate) expression for the kinetic energy operator and in addition the field included only the quadratic and several (small part) of the cubic and quartic force constants. In this work we present a full quartic PES for S 0 thiophosgene (including all 34 quadratic, cubic and quartic force constants), in terms of the symmetrized curvilinear coordinates that were used by MLT [23] and Handy [24] in their work on formaldehyde (different from the coordinates used in our previous work [21] and from those used by Strickler and Gruebele [4]).…”

“…Our earlier empirical field [21], was of limited scope and applicability since our vibrational calculation method involved a simplified (approximate) expression for the kinetic energy operator and in addition the field included only the quadratic and several (small part) of the cubic and quartic force constants. In this work we present a full quartic PES for S 0 thiophosgene (including all 34 quadratic, cubic and quartic force constants), in terms of the symmetrized curvilinear coordinates that were used by MLT [23] and Handy [24] in their work on formaldehyde (different from the coordinates used in our previous work [21] and from those used by Strickler and Gruebele [4]). The field obtained in this work appears to be of good quality, as it was able to reproduce the experimentally measured lower excited vibrational levels (fundamentals, overtones and combinations) in S 0 thiophosgene.…”

High-resolution synchrotron infrared spectroscopy of thiophosgene: The ν2 and ν4 fundamental bands near 500 cm−1

“…Many hundreds of vibrational levels in the ground and excited electronic states have been experimentally observed, allowing the development of detailed anharmonic force fields including all six vibrational modes [4][5][6]. Interestingly, however, there have been no previous systematic high resolution studies of this molecule's vibration-rotation spectrum.…”