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(3+1)-resonantly enhanced multiphoton ionization-photoelectron spectroscopy of the (3d-4s) supercomplex of acetylene : The geometry of the E state revisited through experiment and theory

(3 + 1)-resonance enhanced multiphoton ionization-photoelectron spectroscopy (REMPI-PES) has been carried out via various low vibrational levels of the D, F, and E states belonging to the (3d-4s) supercomplex of acetylene. The photoelectron analysis takes into account the Renner–Teller coupling occurring in the ion ground state. In the 74 500–76 500 cm–1 energy range, the coupling between the F Rydberg state and E valence state is strongly revealed through the photoelectron spectra. Moreover, the vibrational analysis of the REMPI-PES spectra enlighten the controversial geometry of the E valence state. They strongly indicate a planar trans-bent geometry of the E valence state, quantitatively confirmed by an ab initio study. This study confirms the tentative frequencies for the nu1 stretching mode (3307 cm–1 for C2H2+, 2572 cm–1 for C2D2+), as well as the frequencies for the bending mode : trans-nu4 (694 cm–1 for C2H2+, 586 cm–1 for C2D2+) and cis-nu5 (775 cm–1 for C2H2+, 569 cm–1 for C2D2+) of the cations.

doi:10.1063/1.1589480

Voir en ligne : J. Chem. Phys. 119, 3751-3762 (2003)