Electron momentum spectroscopy of valence orbitals of cyclopentene: Nuclear dynamics and distorted wave effect.

We report a measurement of electron momentum distributions of valence orbitals of cyclopentene employing symmetric noncoplanar (e,2e) kinematics at impact energies of 1200 and 1600 eV plus the binding energy. Experimental momentum profiles for individual ionization bands are obtained and compared with theoretical calculations considering nuclear dynamics by harmonic analytical quantum mechanical and thermal sampling molecular dynamics approaches. The results demonstrate that molecular vibrational motions including ring-puckering of this flexible cyclic molecule have obvious influences on the electron momentum profiles for the outer valence orbitals, especially in the low momentum region. For π∗-like molecular orbitals 3a′′, 2a′′, and 3a′, the impact-energy dependence of the experimental momentum profiles indicates a distorted wave effect. [ABSTRACT FROM AUTHOR]