1 B-1(u)-2(1)A(g) conical intersection in trans-butadiene: ultrafast dynamics and optical spectra

The potential-energy functions of the 1 B-1(u) and 2 (1)A(g) excited valenc e states of trans-buradiene have been characterised by the CASPT2 method. B ased on these ah initio data, a vibronic-coupling model describing the coni cal intersection of the 1 B-1(u) and 2 (1)A(g) states has been constructed. UV resonance-Raman and absorption spectra have been calculated, employing the time-dependent approach. The time-dependent wave-packet calculations re produce the expected ultrafast (approximate to 30 fs) radiationless decay o f the optically bright 1 B-1(u) state into the dark 2 (1)A(g) state. (C) 20 00 Elsevier Science B.V. All rights reserved.