The low-lying electronic states of FeO+:: Rotational analysis of the resonance enhanced photodissociation spectra of the 6Π7/2←X 6Σ+ system

The resonance enhanced (1+1) photodissociation spectra of the (8,0) and (9,0) bands of the (6)Pi(7/2)<--(6)Sigma(+) system of FeO+ have been recorded. From a rotational analysis, the rotational parameters for the (6)Sigma(+) ground state of FeO+ have been obtained for the first time. The rotational constant B-0=0.5020+/-0.0004 cm(-1) is derived, giving r(0)=1.643+/-0.001 Angstrom. Other molecular parameters determined for the (6)Sigma(+) ground state are the spin-spin coupling constant, lambda=-0.126+/-0.006 cm(-1), and the spin-rotational coupling constant, gamma=-0.033+/-0.002 cm(-1). The assignment of the upper state as (6)Pi(7/2) is based on the characteristic appearance of the band and on time-dependent density functional (TD-DFT) calculations performed on FeO+. The reliability of the TD-DFT method in the prediction of excited states of FeO+ is corroborated by calculations on CrF and MnO, which have been extensively characterized either by spectroscopy or by high-level theoretical calculations. (C) 2003 American Institute of Physics.