Global fit of rotational transitions of methyl formate (HCOOCH3) in the ground and first excited torsional states

Abstract The microwave spectrum of methyl formate (HCOOCH 3 ) has been observed in the frequency range from 7 to 200 GHz. New 348 lines were assigned to E -species in the first excited torsional state. By combining these lines with previously reported data, a global analysis of A - and E -species lines of the ground and first excited torsional states were carried out on the basis of the internal axis method. A total of 3862 transitions were fitted to a Hamiltonian model involving 69 molecular parameters to a weighted unitless standard deviation of 1.96.