Chan Ryang Park

Photodissociation dynamics of HNO3 at 266 nm

Abstract The photodissociation dynamics of HNO3 at 266 nm has been investigated by measuring laser induced fluorescence spectra of the OH ( 2 п) fragments. The measured fractions of the available energy distributed among the fragements are ƒ t = 0.21, ƒ r ( OH ) = 0.047 , ƒ int ( NO 2 ) = 0.74 , and negligible OH fragments are found in the vibrationally excited states. By analyzing Doppler profiles of the spectra, vector correlations in the photodissociation of HNO3 have been measured. The measured correlations show that the transition is parallel (βμv = 1.0) but the transition dipole moment and the recoil velocity of the fragment are not exactly parallel. The rotational angular momentum J of the product OH is aligned parallel to the recoil direction of the fragment. From the measured correlations and the large fraction of the internal energy in the NO2 fragments, it has been concluded that the transition at 266 nm is described as vibronic to the pyramidal excited state of A″ symmetry. Together with the measured Λ-doublet distribution of the OH fragments, the dynamics of photodissociation is discussed in detail.

Two photon dissociation of acetone, acetaldehyde, and acetic acid at 243 nm: translational energy releases in the H atom channel

The hydrogen atom channels from photodissociation of acetone, acetaldehyde, and acetic acid at 243 nm have been investigated by detecting H atoms using two photon absorption at 243.2 nm and induced fluorescence at 121.6 nm. Translational energies of the H atoms were measured by Doppler broadened H atom spectra. By absorption of two photons at 243 nm, the H atoms were produced from acetyl radicals. The possible dissociation mechanisms are discussed from the measured translational energy releases.

Photodissociation of allyl cyanide at 193 nm

Abstract Photodissociation dynamics of allyl cyanide at 193 nm has been investigated by measuring laser-induced fluorescence spectra of CN fragments. From the spectra, rotational and vibrational energy distributions of CN have been obtained. The measured average rotational energy is 1080, 900 and 760 cm −1 for v″=0,1,2, respectively, and the fraction of the vibrational population is 0.70/0.24/0.06 for v″=0/1/2. The measured distributions are well represented by statistical prior calculations, from which the detailed dissociation dynamics is discussed.

Photodissociation of cyclopropyl cyanide at 193 nm

Photodissociation of cyclopropyl cyanide at 193 nm has been investigated by measuring laser induced fluorescence spectra of CN fragments that are exclusively produced in the ground electronic state. From the spectra, internal energy of CN and translational energy releases in the products were measured. Considering energetics for various product channels, it is concluded that cyclopropyl cyanide dissociates into an allyl and CN radicals resulting from ring opening prior to dissociation.