Rotational Spectra of Symmetric Top Molecules in Ground andDifferent Vibrational Excited States, and Phenomenon of Resonance – Applying in CF3CCH

Masoud Motamedi

doi:10.3390/i8040316

Abstract

This paper deals with review of exploration of resonance in symmetric topmolecules in different vibrational excited states, vt = n (n =1, 2, 3, 4). Calculations for CF3CCH shows that resonance take place at [Eq. 20] and [Eq. 21] for v10 = 2 and v10 = 3 respectively. In order to account for splitting about 3 MHz for the - 2 series in v10 = 4 is necessary to introduce the element {J, k, l |f24| J, k + 2,l − 4} in fitting program.

Highlights

The vibrational spectrum of CF3CCH was assigned by Berney et al [1]
The rotational spectrum in the v10 = 1 state is strong and it is not complicated by interactions with nearby vibrational states
For symmetric top molecules like CF3CCH, the ground vibrational state rotational energies are given up to sextic terms by equation (1) and by application of selection rules ∆J = + 1 and ∆k = 0, the frequencies are given by equation (2)

Summary

Introduction

The vibrational spectrum of CF3CCH was assigned by Berney et al [1]. The energy level of its lowest lying degenerate vibration is only E = 171 cm-1, according to the Boltzman distribution law it has a population of 58% (29%×2 for vibrational degeneracy) of the ground state at dry ice temperature (200 K). For symmetric top molecules like CF3CCH, the ground vibrational state rotational energies are given up to sextic terms by equation (1) and by application of selection rules ∆J = + 1 and ∆k = 0, the frequencies are given by equation (2) The spectra in this state are simple, so the different k values (k = 0,1,2,3,4...) for each J transition are assigned . + t and small (A − B − Aζ = −458 MHz) value it is possible to observe direct l-resonance transitions in the microwave range This is a typical pattern for C3v doubly degenerate states and is predominantly due to the combinations of the splitting of the positive and negative (kl-1) series by l- type resonance [which is inversely proportional to (kl-1)] and the shift to low frequency due to DJk [which is proportional to (kl-1)2]. The main off-diagonal elements are the l-doubling elements equation (6)

Plot of Beff

E-11 E-12 r r

Results and Discussion