(B plus E ⊗ b) ⊗ e Jahn-Teller and pseudo-Jahn-Teller effects in the spiropentane radical cation

In this paper we examine the Jahn-Teller (JT) and pseudo-Jahn-Teller (PJT) effects in the spiropentane radical cation (SP+) by an ab initio quantum dynamical method. Spiropentane (SP) possesses D-2d symmetry at its equilibrium configuration. The two low-lying electronic states of SP+ belong to (X) over tilde B-2(2) and (A) over tilde E-2 symmetry, respectively. SP+ in the degenerate (A) over tilde state is susceptible to JT distortions along the vibrational modes of b symmetry. The (A) over tilde state of SP+ is vertically similar to 0.51 eV spaced from its (X) over tilde state. Symmetry rule allows a coupling of the (X) over tilde and (A) over tilde states via the degenerate e vibrational modes. This is termed as the (B + E circle times b) circle times e JT and PJT effects revealing the symmetry of the electronic states and the coupling vibrational modes. The theoretical findings establish significant impact of the JT and PJT coupling in the observed complex structure of the (X) over tilde-(A) over tilde bands of SP+. (C) 2010 Elsevier B. V. All rights reserved.