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

[1] 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 d(0,0) and d(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.

A theoretical study of the rotational structure of the ϵ(0,0) band of NO

“…This model‐potential approach has proved to be an adequate theoretical tool to supply quantitative values of spectral properties 18, 19 in recent applications that involved electronic and rovibronic transitions to molecular Rydberg states in a variety of molecular species. Recently, we have reported rotational intensities for the γ(0,0), δ(0,0), and δ(1,0) bands of NO 20–22. The present photoabsorption cross section calculations concerning this band at 295 K are, to our knowledge, the first theoretical data supplied.…”

Ab initio simulation of UV/vis absorption spectra for atmospheric modeling: method design for medium-sized molecules

“…The photodissociation rate constant and its dependence on temperature can be measured provided a pure sample is obtained and the absorption cross section at various temperatures is known. 1,2 The pure sample condition becomes increasingly difficult to satisfy as the size, complexity and stability of the compound in question impede attempts to synthesize it. Currently, the absorption cross sections that are used to determine the photodissociation rates of complex or unstable molecules are unknown and are crudely estimated.…”