Abstract :
Theoretical calculations are made for the collision-induced electronic absorption in the atmospheric infrared a)X (0,0) and visible b)X
(0,0) bands of oxygen in O2–N2 and O2–CO2 pairs. We consider only the long-range quadrupolar induction mechanism and use ab initio
values for the quadrupole transition matrix elements that arise from spin-orbit mixing. By fitting the experimental value for the a)X (0,0)
absorption in O2–N2, we obtain estimates for the isotropic and anisotropic polarizability electronic transition matrix elements of O2. As a
check, we then use these results together with other known data to calculate the corresponding absorption for O2–CO2. We find good
agreement, considering experimental error and theoretical approximations. We then estimate the corresponding absorption for the b)X (0,0)
absorption in O2–N2. We discuss briefly the observed collision-induced absorption by O2–O2 pairs, and conclude that there must be other
induction mechanisms involved for this system. Because of the importance of absorption by O2 in the Earth’s atmosphere, we conclude that a
systematic study, including both additional measurements and theoretical analyses must be carried out before a satisfactory understanding
can be attained.
q 2005 Elsevier B.V. All rights reserved
