The (A)over-tilde(2)E/(B)over-tilde(2)B(2) photoelectron bands of allene beyond the linear coupling scheme: An ah initio dynamical study including all fifteen vibrational modest

In an earlier publication [J. Chem. Phys. 1999, 111, 10452] we theoreticall y investigated the photoelectron spectrum of allene (C3H4+) pertinent to th e (A) over tilde E-2/(B) over tilde B-2(2) interacting electronic manifold of its radical cation (C3H4+). Employing a linear vibronic coupling scheme it was demonstrated that in addition to the E circle timesB Jahn-Teller act ivity within the 2e electronic manifold, there is a strong (E circle timesB ) + E pseudo-Jahn-Teller interaction with the (B) over tilde B-2(2) electro nic state, which causes the diffuse structures observed at high energies. H ere, the same photoelectron spectrum is reinvestigated including all fiftee n vibrational degrees of freedom of the system and a higher order coupling scheme. The coupling parameters of the Hamiltonian are calculated by ab ini tio methods. The photoelectron band is calculated by the wave packet propag ation method within the multiconfiguration time-dependent Hartree (MCTDH) s cheme and compared with the experimental results of Baltzer et al. [Chem. P hys. 1995, 196, 551]. The progressions at low energies are identified unamb iguously by calculating the "stick" vibronic spectrum within the (A) over t ilde E-2 electronic manifold, considering five relevant vibrational modes, and the effect of the higher order couplings is clearly demonstrated. The c alculations show that it is necessary to re-assign the progressions in the low-energy region of the spectrum to the vibrational mode nu (3), which is of C=C stretching and H-C-H bending character and the combination of symmet ric (nu (2)) and antisymmetric (nu (7)) H-C-H bending vibrational modes. In addition, we report on the time-dependent nuclear dynamics by snapshots of the time-evolved wave packet and by the diabatic electronic populations.