Theoretical and experimental pressure shifts in some select rotational transitions of the methyl cyanide molecule

The Anderson–Tsao–Curnutte–Frost and Murphy–Boggs theories of linewidth and line shift are briefly discussed, and the significance of certain ’’resonance’’ functions is noted. Power series approximations for these functions, which facilitate numerical evaluation of linewidths and line shifts using these two theories, are given and discussed. For completness, experimental line shift parameters for several rotational transitions in the CH3C14N and CH3C15N molecules are presented with a comparison of the theoretical results derived using the Murphy–Boggs and the modified Anderson theories.