The microwave spectra of propyne in the 17–70 GHz region for the ground V1=1 and V9=1 vibrational states

Abstract

The rotational spectra of the ground V₁₀=1 and V₉=1 vibrational states of propyne have been determined for the frequency range of 17–70 GHz. The ground and V₁₀=1 measurements have been shown to be in excellent agreement with constants derived from higher J values by other authors. This was the first time that a sufficient number of lines in the V₉=1 state had been measured to make a reasonable assignment. It was found that the data could be fit to Amat’s theory for V_t=1 states in C_3V molecules only if an additional term of 0.653 (J+1) was added to the frequencies predicted for the K=±1, l=∓1 lines. Our assignments are in disagreement with those of Jaseja based only on the J=2→3 transitions measured by Gordy. Our data completes the low J rotational spectra for the ground V₁₀=1 and V₉=1 states of CH₃CCH.