Photolysis wavelength dependence of the translational anisotropy and the angular momentum polarization of O2(aΔg1) formed from the UV photodissociation of O3

Abstract

The translational anisotropy and angular momentum polarization of the O(2)(a (1)Delta(g),v = 0;J = 15-27) molecular photofragment produced from the UV photodissociation of O(3) in the range from 270 to 300 nm have been determined using resonance-enhanced multiphoton ionization in conjunction with time-of-flight mass spectrometry. At the shortest photolysis wavelengths used, the fragments exhibit the anisotropic vector correlations expected from a prompt dissociation via the (1)B(2) <--(1)A(1) transition. Deviations from this behavior are observed at longer photolysis wavelengths with, in particular, the angular momentum orientation showing a significant reduction in magnitude. This indicates that the dissociation can no longer be described by a purely impulsive model and a change in geometry of the dissociating molecule is implied. This observation is substantiated by the variation of the translational anisotropy with photolysis wavelength. We also observe that the bipolar moments describing the angular momentum polarization of the odd J states probed are consistently lower in magnitude than those of the even J states and that this variation is observed for all photolysis wavelengths.

Origin of the “odd” behavior in the ultraviolet photochemistry of ozone

“…Hancock et al were the first to report even-odd alternations in O 2 (a 1 Δ g ) photofragment vector correlations, and found that following the 270-nm photolysis of ozone at 140 K, the μ-j and v-j angles were smaller for the odd fragments than for the even fragments (7). Similar results have been reported for the photolysis of 140 K ozone at multiple wavelengths (8,13,15), and for the 266-nm photolysis of ozone at 70, 115, and 170 K (33). One explanation for the observed alternation is differences in the formation of the A′ and A′′ Λ-doublets.…”

“…In addition to the rotational population alternation, even-odd alternations in the vector correlations of the O 2 (a 1 Δ g ) fragments have been previously measured (7,8,13,15). Vector correlations describe the average angles between the transition dipole moment (μ), fragment recoil velocity vector (v), and fragment angular momentum vector (j), and can provide a window into photodissociation dynamics.…”

“…ozone | photochemistry | quantum dynamics | isotopic fractionation | lambda doublets G iven the importance of the stratospheric ozone layer in protecting the earth from harmful ultraviolet (UV) rays (1), it is not surprising that the UV photodissociation of ozone has been the subject of numerous experimental (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) and theoretical studies (16)(17)(18)(19)(20)(21)(22)(23)(24). In the strongly absorbing Hartley band (200-300 nm), the photodissociation involves two low-lying excited states with the same symmetry (A′) as the ground state (X): the B state which diabatically correlates to O 2 (a 1 Δ g ) and O( 1 D) products, and the R state which diabatically correlates to O 2 (X 3 Σ − g ) and O( 3 P) products.…”

New theoretical investigations of the photodissociation of ozone in the Hartley, Huggins, Chappuis, and Wulf bands

“…translational anisotropy and angular momentum alignment) yield additional and more detailed information about the fragmentation dynamics. [111][112][113][114] Of course, the calculation of such quantities is much more demanding, but still tractable with our present day knowledge of the PESs involved. In order to understand the unusual isotopic fractionation of ozone in the atmosphere 115 isotopic effects in photodissociation are important.…”

Three-Body Breakup in the Dissociative Recombination of the Covalent Triatomic Molecular IonO3+

“…It has also been realized that the ozone cation and anion deserve attention since the ozone neutral, positive, and negative chemistry could affect each other in unanticipated ways [3]. In comparison with the vast literature on neutral ozone, not least its photochemical properties (see, e.g., [4,5]), work on the ozone cation is sparse [6], but definitely needed for an understanding of the O 3 ion chemistry in the stratosphere and lower ionosphere. It is worth noting that ozone has also been detected in the polar regions of Mars [7] and on the Jovian satellite Ganymede [8].…”