Correlation Between The Shape And The Excitation Of The Angular Momentum For The Hcn/hnc Molecule

Abstract

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The [H,C,N] molecular system with the two linear isomers, HCN and HNC, is one of the most important model systems where it is possible to conduct eigenstate-resolved studies that encode the internal dynamics of strongly bound molecules at excitation energies relevant for chemical reactions.

The geometric shape of a molecule in its vibrationless state is an intuitive and useful chemical concept. In highly excited vibrational states we expect a significant change of this molecular shape. For triatomic linear HAB molecules this change depends on the two stretching and the bending vibrational excitations.

In highly excited bending states a fourth dynamical parameter becomes important: the vibrational angular momentum, $l$. The corresponding classical picture is the rotation of the hydrogen atom around the A-B core figure axis. The highest possible excitation for a given $(v_2,l)$ bending state is the state with $l=v_2$. These are the states for which we expect the most significant dynamical effects due to the vibrational angular momentum.

In this work we study the correlation between the molecular shape and the rovibrational eigenenergies of the [H,C,N] molecule in the $v_1 v_2^{v_2} v_3$ states with the highest possible excitation of the vibrational angular momentum. The eigenergies we use have been measured using infrared HOTGAME (HOT GAs Molecular Emission) spectroscopy or come from the vibrational assignment of \textit{ab initio} energy lists.