Absorption Cross Section of Ozone Isotopologues Calculated with the Multiconfiguration Time-Dependent Hartree (MCTDH) Method: I. The Hartley and Huggins Bands † Steve Alexandre Ndengue ´ Laboratoire de Spectrome ´trie Physique, UniVersite ´ Joseph Fourier, 38402 St. Martin d’He `res, France Fabien Gatti CTMM, Institut Charles Gerhardt, UMR 5253, CC 1501, UniVersite ´ de Montpellier II, F-34095 Montpellier, Cedex 05, France Reinhard Schinke Max Planck Institut fu ¨r Dynamik und Selbstorganisation, D-37073 Go ¨ttingen, Germany Hans-Dieter Meyer Im Neuenheimer Feld 229, Theoretische Chemie, Physikalisch-Chemisches Institut, UniVersita ¨t Heidelberg, Germany Re ´my Jost* Laboratoire de Spectrome ´trie Physique, UniVersite ´ Joseph Fourier, 38402 St. Martin d’He `res, France ReceiVed: April 12, 2010; ReVised Manuscript ReceiVed: June 8, 2010 The absorption cross sections of 18 isotopologues of the ozone molecule have been calculated in the range of the Hartley-Huggins bands (27000-55000 cm -1 ). All 18 possible ozone isotopologues made with 16 O, 17 O, and 18 O have been considered, with emphasis on those of geophysics interest like 16 O 3 17 O 16 O 2 , 16 O 17 O 16 O, 18 O 16 O 2 , and 16 O 18 O 16 O. We have used the MCTDH algorithm to propagate wavepackets. As an initial wavepacket, we took the vibrational ground state multiplied by the transition dipole moment surface. The cross sections have been obtained from the autocorrelation function of this wavepacket. Only two potential energy surfaces (PESs) and the corresponding transition dipole moment are involved in the calculation. The dissociating R state has been omitted. The calculations have been performed only for J ) 0. The comparison with the experimental absorption cross sections of 16 O 3 and 18 O 3 has been performed after an empirical smoothing which mimics the rotational envelop. The isotopologue dependence of the cross sections of 18 isotopologues can be split into two energy ranges, (a) from 27000 to 32000 cm -1 , the Huggins band, which is highly structured, and (b) from 32000 to 55000 cm -1 , the main part of the cross section which has a bell shape, the Hartley band. This bell-shaped envelop has been characterized by a new analytic model depending on only four parameters, amplitude, center, width, and asymmetry. The isotopologue dependence of these parameters reveals the tiny differences between the absorption cross sections of the various isotopologues. In contrast to the smooth shape of the Hartley band, the Huggins band exhibits pronounced vibrational structures and therefore shows large isotopologue differences which may induce a significant isotopologue dependence of the ozone photodissociation rates under actinic flux. 1. Introduction The anomalous isotopologue (or isotopomer) ratios observed in stratospheric ozone 1 are attributed to strong isotope selectivity during the Chapman formation process. 2 In summary, the formation of asymmetric isotopologues (or isotopomers) like 17 O 16 O 16 O and 18 O 16 O 16 O is favored 3–6 compared with the formation of symmetric isotopologues (or isotopomers) like 16 O 17 O 16 O, and 16 O 18 O 16 O. 7 However, an additional selectivity during photodissociation processes cannot be ruled out. This selectivity can be due to the differences between the absorption cross section of various isotopologues and/or to asymmetric branching ratios during the photodissociation of asymmetric isotopologues In contrast, the symmetric isotopologues 16 O 17 O 16 O and 16 O 18 O 16 O are expected to photodissociate into only asymmetric oxygen molecules † Part of the “Reinhard Schinke Festschrift”. * To whom correspondence should be addressed. E-mail: rjost@ spectro.ujf-grenoble.fr. 17 O 16 O 2 + hν f 17 O 16 O + 16 O or 16 O 16 O + 17 O (1) 18 O 16 O 2 + hν f 18 O 16 O + 16 O or 16 O 16 O + 18 O (1′) J. Phys. Chem. A 2010, 114, 9855–9863 9855 10.1021/jp103266m  2010 American Chemical Society Published on Web 06/28/2010