Microwave-microwave double-resonance spectroscopy of acetone in the torsional excited state ν17

Abstract

Since rotational transitions between energy levels with low rotational quantum numbers J have not been identified in previous investigations of the rotational spectrum in the ν17 state of acetone, such transitions have now been searched for and assigned by microwave-microwave double-resonance spectroscopy. Eventually, 15, 23, 4 and 0 transitions have been found in the (00) = AA, (01) = EE, (11) = AE and (12) = EA torsional substates, respectively. Even though the dimensionless standard deviation of the least-squares fit of the parameters of the Effective Rotational Hamiltonian (ERHAM) to their frequencies combined with those used in earlier work increased by ≈ 23%, the standard errors of most spectroscopic parameters decreased by more than 20%, but increased for others, probably due the changes in fitting blended transitions. A comparison of the results with those of other recent investigations of acetone confirms that the ERHAM code is unable to fit the ν17 state of acetone without accounting for the interactions with other vibrational states.