Photodissociation of ozone at 193 nm by high-resolution photofragment translational spectroscopy

Abstract

The photodissociation of ozone has been studied at 193 nm using high resolution photofragment translational spectroscopy. The results show six distinct peaks in the time-of-flight spectra for the O2 product and its momentum-matched O atom counterpart. The translational energy distributions determined from the time-of-flight spectra reveal the production of a range of electronic states of the photofragments. The product electronic states were identified based on the translational energy distributions, with the aid of state-resolved imaging experiments by Houston and co-workers. The results reveal the production of a substantial yield of highly excited triplet states of O2, recently suggested to play an important role in the stratospheric ozone balance. In addition, peaks corresponding to O2(a 1Δg) and O2(b 1Σg+) were observed, the latter confirming a previous report [A. A. Turnipseed et al., J. Chem. Phys. 95, 3244 (1991)]. Evidence was seen for a small contribution from the triple dissociation O3→3O(3P), and insight into the dissociation dynamics for this process was inferred from the translational energy distributions. Branching fractions and angular distributions were measured for all channels. The latter were found in general to yield negative β parameters, in contrast to what is seen at longer wavelengths.

Photofragment imaging by sections for measuring state-resolved angle-velocity differential cross sections

“…There have been several previous reports of ozone photodissociation studies by some form of photofragment translational energy spectroscopy or Doppler spectroscopy. [52][53][54][55][56] Whereas there is reasonable consistency in the reported fragment velocity distributions, the measured anisotropies show significant variations, only part of which can be attributed to different excitation conditions.…”

Reactivity and electronic states of O4 along minimum energy paths

“…Another source of interest is the possible relevance of highly vibrationally excited states in determining the chemical composition of the atmosphere. This issue has been the subject of great interest and debate recently, [2][3][4][5][6][7][8][9] particularly in relation to the possibility of producing ozone from highly vibrationally excited O 2 molecules and considering that highly vibrationally excited O 2 molecules are known to be formed during the photodissociation of ozone in its triplet channel: 3,5 …”

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

“…It is likely that the repulsive curves through which the DR proceeds are also important for the photodissociation of O 3 , especially when the photon energy is close to the ionization limit. Indeed, for the photon energy of 193 nm which lies 0.16 eV above the O 3 P O 3 P O 3 P limit, the three-body channel constitutes 2% [34], while for the photon energy of 157.6 nm the three-body channel is observed to be comparable to the two-body channel [35]. Moreover, the results concerning the dynamics of the three-body breakup of the ozone initiated by 193 nm photon are similar to our observation; i.e., the synchronous fragmentation proceeds through almost linear geometry [34].…”

“…Indeed, for the photon energy of 193 nm which lies 0.16 eV above the O 3 P O 3 P O 3 P limit, the three-body channel constitutes 2% [34], while for the photon energy of 157.6 nm the three-body channel is observed to be comparable to the two-body channel [35]. Moreover, the results concerning the dynamics of the three-body breakup of the ozone initiated by 193 nm photon are similar to our observation; i.e., the synchronous fragmentation proceeds through almost linear geometry [34]. The analogy between photodissociation and dissociative recombination, however, should not be taken too far.…”