We have used velocity map ion imaging to measure the angular anisotropy of the NO (A) products from the photodissociation of the N2–NO complex. Our experiment ranged from 108 to 758 cm–1 above the threshold energy to form NO (A) + N2 (X) products, and these measurements reveal, for the first time, a strong angular anisotropy from photodissociation. At 108 cm–1 above the photodissociation threshold, we observed NO (A) photoproducts recoil preferentially perpendicular to the laser polarization axis with an average anisotropy parameter, β = −0.25; however, as the available energy was increased, the anisotropy increased, and at 758 cm–1 above the threshold energy, we found an average β = +0.28. The observed changes in the angular anisotropy of the NO (A) photoproduct are qualitatively similar to those observed for the photodissociation of the Ar–NO complex and likely result from changes in the region of the excited state potential energy surface accessed during the electronic excitation. At the lowest available energy, we also noted a large contribution from hotband excitation; however, this contribution decreased as the available energy increased. The outsized contribution at the lowest available energy may result from hotbands having better Franck–Condon overlap with the excited electronic state near threshold. Finally, we contrast the experimental center of mass translational energy distribution with a statistical energy distribution determined from phase space theory. The experimental and statistical distributions show pronounced disagreement, particularly at low kinetic energies, with the experimental one showing less dissociation resulting in high rotational levels of the fragments.

We have recorded the resonance-enhanced multiphoton ionization spectrum for NO (A) products from photodissociation of the N2-NO complex. We made measurements at excitation energies ranging from 28 to 758 cm–1 above the threshold to produce NO (A) + N2 (X) products, and the resulting spectra reveal the NO (A) rotational states formed during dissociation, allowing us to determine the rotational state distribution. At the lowest available energies, 28 and 50 cm–1 above threshold, we observed contributions from NO (A) rotational states that exceed the available energy and must originate from excitation due to hotbands of the complex. At all higher energies, we did not observe any energetically disallowed NO (A) rotational states, and for all available energies above 259 cm–1 the observed rotational transitions do not extend to the maximum allowed by energy conservation. Furthermore, the observed distributions were typically biased toward low rotational states, in contrast with expectations from vibrational predissociation. From the rotational state distributions, we determined the average fraction of energy partitioned into NO (A) rotation, f NO rot, ave, to be 0.088 at the highest available energy, and this fraction increased as the available energy decreased. By combining the average NO (A) rotational energy along with the average center-of-mass translational energy from our previous work, we determined the average rotational energy for the undetected N2 (X) photoproduct. The results showed that the N2 fragment has a higher average rotational energy relative to the NO fragment. Finally, we found that the NO (A) rotational state distribution was colder than expected for a statistical dissociation.