15min:

ANDREI DEEV, KANA TAKEMATSU, DAVID J. ROBICHAUD, MITCHIO OKUMURA, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena CA 91125; JOHN F. STANTON, Department of Chemistry, University of Texas, Austin, TX, 78712.

The Jahn-Teller Effect in the lowest excited states of the nitrate radical NO₃ remains poorly understood. In this paper, we examine the first excited state, A~² E'', in a joint experimental and theoretical study. The forbidden A~² E'' X ~² A₂' transition is recorded by Near Infrared Cavity Ringdown Spectroscopy (CRDS) at medium resolution from 6000 to >10,000 cm^-1, extending and refining our preliminary results. We observe over 30 major vibronic bands, most with resolvable rotational structure. Tentative assignments are made on the basis of high level EOMIP-CCSD(T) calculations of the vibronic Hamiltonian, which includes up to quartic terms. Our results indicate that the A state undergoes static Jahn-Teller distortion, with strong vibronic coupling among both degenerate modes and the symmetric stretch. The Jahn-Teller effect in NO₃ appears to be complex and unusual, and remains a difficult but fascinating challenge.