Large scale variational calculations on the vibrational level structure and vibrational mixing in S0 HDCO up to very high excitation energies

Abstract

We perform converged high precision variational calculations to determine the exact energies of all vibrational states in S0 HDCO, extending up to 10000cm−1 of vibrational excitation energy. We also explore the resonances and intermode couplings in this energy range. We compare the calculated level structure to the recently measured frequencies by Ellsworth et al. [K.K. Ellsworth, B.D. Lajiness, J.P. Lajiness and W.F. Polik, J. Mol. Spectrosc. 252 (2008) 205] in order to check their assignments and further clarify the vibrational mixing pattern and vibrational resonances in HDCO, that are very different from the other more symmetric formaldehyde species H2CO and D2CO. For the calculations we use our specific vibrational method (recently employed for extensive vibrational studies on H2CO and D2CO), consisting of a combination of a search/selection algorithm and a Lanczos iteration procedure and based on the Martin, Lee, Taylor potential energy surface for formaldehyde, allowing to extend the calculations up to very high vibrational excitation energies.