Imaging HNCO photodissociation at 201 nm: State-to-state correlations between CO (X1Σ+) and NH (a1Δ)

Abstract

The NH(a1Δ)+CO(X1Σ+) product channel for the photodissociation of isocyanic acid (HNCO) on the first excited singlet state S1 has been investigated by means of time-sliced ion velocity map imaging technique at photolysis wavelengths around 201 nm. The CO product was detected through (2+1) resonance enhanced multiphoton ionization (REMPI). Images were obtained for CO products formed in the ground and vibrational excited state (v=0 and v=1). The energy distributions and product angular distributions were obtained from the CO velocity imaging. The correlated NH(a1Δ) rovibrational state distributions were determined. The vibrational branching ratio of 1NH (v=1/v=0) increases as the rotational state of CO(v=0) increases initially and decreases afterwards, which indicates a special state-to-state correlation between the 1NH and CO products. About half of the available energy was partitioned into the translational degree of freedom. The negative anisotropy parameter β indicates that it is a vertical direct dissociation process.