ASSIGNMENT OF A COMBINATION STATE $v_{t} = 1 + v_{t}{'} = 1$ of $(H_{3}CO)_{3}$

Abstract

Trioxane molecule $(H_{2}CO)_{3}$ permits us to observe rotational spectra of an excited state $v_{t} = 1+ v_{t}^{\prime} =1$ the vibrational energy for which is located at $832\, cm^{-1}$ from the ground state. Microwave transitions have been measured in the frequency range 60 up to 140 GHz, that is to say for values of the quantum number J going from 6 to 13. Analysis of the spectra relies on the hypothesis that there is no accidentally strong resonance between the vibrational states concerned and thus the expressions reported by TARRAGO can be used. Most precisely the assignment is made from the splitting of the $K = 0, \Sigma_{t} \ell_{t} = 0$ transitions. Accurate parameters are obtained by a direct diagonalization of the energy matrix and a least squares procedure. Most of the observed frequencies agree with the calculated ones.""