Predissociation of the NH/ND(c 1Π,v′,J′) states

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Abstract
The predissociation of the electronically excited NH/ND(c 1Π) state was studied by accurate lifetime measurements. The pulsed generation of single rotational states of different vibrational levels was performed by dye laser excitation in the NH/ND c 1Π–a 1Δ band system. The lifetime of ND(c,v’=0,J’=1) is 500±10 ns. This value is close to the purely radiative lifetime of the rotationless state. The lifetime increases steadily up to J’=15. The lifetime of ND(c,v’=1) is 235 ns for very low J’ and decreases for higher J’. These shorter lifetimes are due to predissociation by the repulsive 1 5Σ− state. Similarly, the NH(c,v’=0) state is predissociated for all J’, having an average lifetime of 463 ns for J’=1–7. For J’>7, the lifetime decreases steadily. The lifetime of NH(c,v’=1) is dominated by predissociation, with values near 65 ns for J’=1–6. These experimental results are found to be in very good agreement with an ab initio electronic structure calculation of the radiative and predissociative decay rates.