Characterization of the X~2A_1 (0,0,0) ground vibronic state of CH_2~+ by pulsed-field-ionization zero-kinetic-energy photoelectron spectroscopy

摘要

The rotational structure of the X~2A_1 (0,0,0) ground vibronic state of CH_2~+ has been observed by pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photolectron spectroscopy. Rotational levels with asymmetric top rotational quantum numbers N~+<=5 and K_a~+<=2 have been used to derive a purely experimental r_0 structure [r_(CH)=(1.1049(+-)0.0041) A, alpha_(HCH)=(139.77(+-)0.27) degrees]. Whereas the positions of the K_a~+=0 and 1 levels are in good agreement with previous results, the positions of the K_a~+=2 levels, which are observed for the first time, suggest that the theoretical description of the bending potential and of the Renner-Teller effect in CH_2~+ could still be refined. The single photon photoionization dynamics of the CH_2 X~3B_1 ground state is also consistent with a bent geometry for the ground state of CH_2~+. First PEI-ZEKE photoelectron spectra of CD_2 are also presented.