Abstract
Rovibrational eigenenergies of HONO are computed and compared to experimental energies available in the literature. For their computation, we use a previously developed potential energy surface (PES) and a newly derived exact kinetic energy operator (KEO) including the overall rotation for a tetra-atomic molecule in non-orthogonal coordinates. In addition, we use the Heidelberg Multi-Configuration Time-Dependent Hartree (MCTDH) package. We compare the experimental rovibrational eigenvalues of HONO available in the literature with those obtained with MCTDH and a previously developed potential energy surface (PES) [F. Richter et al., J. Chem. Phys., 2004, 120, 1306.] for the cis geometry. The effect of the overall rotation on the process studied in our previous work on HONO [F. Richter et al., J. Chem. Phys., 2007, 127, 164315.] leading to the cis→trans isomerization of HONO is investigated. This effect on this process is found to be weak.
Highlights
In previous papers, it was demonstrated that the Heidelberg package[8] of the Multi-Configuration Time Dependent Hartree (MCTDH) algorithm[9,10,11,12] is an efficient tool to investigate IVR in relatively large systems such as toluene[13] and fluoroform (9 degrees of freedom),[14] HFCO,[15] DFCO,[16] and H2CS.[17]
We still do not take into account the rotational transitions by absorption of light, i.e. J remains a good quantum number and we do not allow transitions from J to J0, with J0 a J. We will investigate these rotational transitions in future works but in the present paper we focus on another important aspect of dynamics: we include the fact that the molecules can rotate and that the mode specificity for the process studied in ref. 20 can be influenced by rotation
We have checked that the numerical values of all the functions Gij(q) and Vextra(q) at several non-symmetrical grid points, q, agree with those provided by the program TNUM.[43]. The implementation of this kinetic energy operator (KEO), including the overall rotation for a tetra-atomic molecule in non-orthogonal coordinates, in the Heidelberg MCTDH package is an important result of the present work, since this operator could be useful for many systems in the future
Summary
It was demonstrated that the Heidelberg package[8] of the Multi-Configuration Time Dependent Hartree (MCTDH) algorithm[9,10,11,12] is an efficient tool to investigate IVR in relatively large systems such as toluene[13] (reduced to 9 degrees of freedom) and fluoroform (9 degrees of freedom),[14] HFCO,[15] DFCO,[16] and H2CS.[17]. We have predicted that HONO isomerizes in the gas phase with a yield of about 10 percent when the suggested parameters for the pulse are used This result is remarkable given the fact that it is not the reaction coordinate that is excited by the laser pulse but mainly the central ON stretching mode of vibration. We still do not take into account the rotational transitions by absorption of light, i.e. J remains a good quantum number and we do not allow transitions from J to J0, with J0 a J We will investigate these rotational transitions in future works but in the present paper we focus on another important aspect of dynamics: we include the fact that the molecules can rotate and that the mode specificity for the process studied in ref.
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