The C2H photodissociation processes have been studied usingabinitiomultireference perturbative configuration interaction methods. The calculated structural parameters of the two linear lowest lying statesXthinsp;2Sgr;+andAthinsp;2Pgr; were found to be in good agreement with previous theoretical and experimental works. Construction of the correlation diagram indicates that C2H cannot photodissociate into C+CH. Therefore, twohyphen;dimensional potential energy surfaces of the six lowest lyingArsquo;andAlsquo;doublet states have been calculated as functions of the bond angle and the Cndash;H bond distance, keeping the Cndash;C distance at the equilibrium C2H value. It appears that the 1thinsp;2Arsquo;, 2thinsp;2Arsquo;, and 1thinsp;2Alsquo;states correlating to theXthinsp;2Sgr;+andAthinsp;2Pgr; states in linear geometry remain bound at all angles, whereas the 3thinsp;2Arsquo;, 4thinsp;2Arsquo;, and 4thinsp;2Alsquo;are dissociative. However, the structure of the energy surfaces is complicated by the presence of numerous avoided crossings between these states. Transition dipole moments connecting the excited states with theXthinsp;2Sgr;+andAthinsp;2Pgr; states have been also obtained in linear geometry. They were calculated to be very weak, leading to the conclusion that the photodissociation rate of C2H will be negligible below 7 eV. Higher lying states, including Rydberg states, were not considered here, since they cannot dissociate directly into C2+H.
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