Abstract
Rotationally resolved resonance enhanced multiphoton ionisation spectra of the B̃(1)E'' state of NH2D are presented and analysed. The analysis indicates a small (34.9 cm(-1)) lifting of the vibronic degeneracy of the zero point level, approximately equal in sign but opposite in magnitude to the splitting observed in NHD2 in previous work. This observation is consistent with previous measurements on systems with partial isotopic substitution subject to a mild Jahn-Teller effect. A model is developed to calculate the splitting induced by asymmetric isotopic substitution of a degenerate electronic state, based on a harmonic force field with linear and quadratic Jahn-Teller terms added. The force field is developed in internal co-ordinates to allow the same parameters to be used to calculate the pattern of vibronic levels for all four isotopologues. The lifting of the degeneracy of the zero point level on asymmetric substitution comes from the quadratic Jahn-Teller effect; the linear term does not lift the degeneracy.
Highlights
The Jahn–Teller effect is an important consideration in understanding the structure and spectroscopy of degenerate electronic states
In the current paper we present a set of spectra of the B1E00 state of NH2D to complement our earlier spectra of NHD2, and look at relating the Jahn–Teller effects in all four isotopologues by developing a simple model for the force field in internal coordinates that can be applied without adjustment to all four species
The model developed to analyse the rotational structure in the B1E00 state of NHD2 has been successfully applied to NH2D, and confirms the validity of the model, and that for cases of a mild Jahn–Teller effect the formal lifting of the degeneracy by partial isotopic substitution leaves significant terms in the Hamiltonian mixing the two components of the state that must be included for a satisfactory simulation of the rotational structure
Summary
The Jahn–Teller effect in the presence of partial isotopic substitution: the B1E00 state of NH2D and NHD2†. The analysis indicates a small (34.9 cmÀ1) lifting of the vibronic degeneracy of the zero point level, approximately equal in sign but opposite in magnitude to the splitting observed in NHD2 in previous work. This observation is consistent with previous measurements on systems with partial isotopic substitution subject to a mild Jahn–Teller effect. A model is developed to calculate the splitting induced by asymmetric isotopic substitution of a degenerate electronic state, based on a harmonic force field with linear and quadratic Jahn–Teller terms added. The lifting of the degeneracy of the zero point level on asymmetric substitution comes from the quadratic Jahn–Teller effect; the linear term does not lift the degeneracy
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
