Photodissociation of the δ(0,0) and δ(1,0) bands of nitric oxide in the stratosphere and the mesosphere: A molecular‐adapted quantum defect orbital calculation of photolysis rate constants

Abstract

The availability of data concerning the upper atmosphere is essential for an understanding of both the change in solar activity on the Earth and of the different processes that have direct effects on the biosphere, in particular those with harmful environmental consequences. The main goal of the present work is the theoretical analysis of the photodissociation of nitric oxide (NO), which plays an important role in the chemical and energetic balance of the upper atmosphere. Given that the molecular absorption cross section is directly linked to the photodissociation rate of the molecule, we have first determined photoabsorption cross sections and then used the calculated values to obtain the rate constants for the photodissociation processes. The photodissociation of NO at a given wavelength range is triggered by the predissociation of the δ(0,0) and δ(1,0) bands. Through the analysis of the predissociation rate constants, a study of the dissociative behavior of NO by absorption of light within the VUV spectral region has been performed. The dependence on the altitude arises from the temperature changes to the doppler‐broaded halfwidth, in addition to the state population, and the solar zenith angle of the atmospheric photodissociation rate constants of this molecule have been calculated with the molecular‐adapted quantum defect orbital (MQDO) approach. Altitudes ranging from 20 to 90 km, which comprise the stratosphere and mesosphere, have been considered.