Open AccessA semianalytic model for photo‐induced isotopic fractionation in simple molecules
Author(s) -
Liang MaoChang,
Blake Geoffrey A.,
Yung Yuk L.
Publication year - 2004
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2004jd004539
Subject(s) - isotopomers , isotopologue , fractionation , isotope fractionation , isotope , triatomic molecule , photodissociation , kinetic isotope effect , mass independent fractionation , stratosphere , diatomic molecule , deuterium , molecule , chemistry , physics , atomic physics , nuclear physics , meteorology , photochemistry , organic chemistry
We have developed a semianalytic model for computing the photo‐induced isotopic fractionation in simple molecules of interest to the atmospheric science community. The method is based on the Born‐Oppenheimer approximation and the Reflection Principle. It has the main advantage of using commonly available input data, namely, the photolysis cross sections for the standard isotopologue/isotopomer and the ground state isotope‐specific spectroscopic constants. The isotopic fractionation arises principally from the spectral shift induced by the small difference in zero point energy between isotopologues/isotopomers and the contraction of the wave function due to heavier isotope substitution. The latter effect dominates photolytic fractionation away from the cross section maxima. Our new approach is demonstrated with applications to the diatomic molecules HCl and HI, and the triatomic molecules N 2 O and O 3 . Agreement between the model and measurements is excellent. New modeling results for the fractionation of 15 N 15 N 16 O in the stratosphere using the Caltech/JPL two‐dimensional model are presented.