title: Rovibrational spectroscopy using a kinetic energy operator in Eckart frame and the multi-configuration time-dependent Hartree (MCTDH) approach.
abstract: For computational rovibrational spectroscopy the choice of the frame is critical for an approximate separation of overall rotation from internal motions. To minimize the coupling between internal coordinates and rotation, Eckart proposed a condition ["Some studies concerning rotating axes and polyatomic molecules," Phys. Rev. 47, 552-558 (1935)] and a frame that fulfills this condition is hence called an Eckart frame. A method is developed to introduce in a systematic way the Eckart frame for the expression of the kinetic energy operator (KEO) in the polyspherical approach. The computed energy levels of a water molecule are compared with those obtained using a KEO in the standard definition of the Body-fixed frame of the polyspherical approach. The KEO in the Eckart frame leads to a faster convergence especially for large J states and vibrationally excited states. To provide an example with more degrees of freedom, rotational states of the vibrational ground state of the trans nitrous acid (HONO) are also investigated.
authors.affiliation: Theoretische Chemie, Ruprecht-Karls-Universität, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany.
authors.forename: Keyvan
authors.initials: K
authors.lastname: Sadri
authors.affiliation: CNRS, Laboratoire de Chimie Physique (UMR 8000), Université Paris-Sud, F-91405 Orsay, France.
authors.forename: David
authors.initials: D
authors.lastname: Lauvergnat
authors.affiliation: CTMM, Institut Charles Gerhardt (UMR 5232), CC 1501, Université Montpellier II, F-34095 Montpellier Cedex 05, France.
authors.forename: Fabien
authors.initials: F
authors.lastname: Gatti
authors.affiliation: Theoretische Chemie, Ruprecht-Karls-Universität, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany.
authors.forename: Hans-Dieter
authors.initials: HD
authors.lastname: Meyer