A New Interstellar Line: the 5_{1}-4_{0} (E_{2}) Transition in Methyl Alcohol

An emission line has been detected at 84.5 GHz in the direction of the radio continuum source Sgr B2. The new line frequency has been found to coincide with a laboratory measurement of the 5i-4o ( 2) transition of methyl alcohol (CH2OH). Calculations of the spontaneous emission rates from all energy levels of astrophysical interest have been performed; these indicate that not only the 5i-4o (E2) transition in Sgr B2 but also the AJ = 0, AK = 1(E1) transitions discovered in Orion A by Barrett et al. are likely to have population inversions. Additional searches for NH2CN, HCP, CH2Cl, ClCN, FeO, HC3HO, and NH2HCO were carried out in the 80-92-CiHz region without success.