New insights into the Jahn–Teller effect in NO₃via the dark ò<i>E</i>″ state

Abstract

The recent cavity ringdown (CRD) measurement of the forbidden 2 E X 2 A 2 transition of the nitrate radical NO 3 reveals a rich, well-resolved spectrum in the near-infrared. The spectroscopic detail provides a new window onto the Jahn-Teller (JT) and pseudo-Jahn-Teller (PJT) effects in NO 3 . This paper reviews the current experimental evidence for vibronic coupling in the state and discusses the theoretical issues in the context of new preliminary EOMIP/CCSD and CCSD(T) calculations. The theoretical results to date indicate that the 2 E state of NO 3 undergoes a relatively strong JT distortion which may require inclusion of higher order vibronic couplings. The intensity of this transition may involve multiple intensity borrowing mechanisms via PJT coupling among the X , and B states.