Photodissociation dynamics of organic halides and proposal of a new portable membrane-inlet based time-of-flight mass analyzer for their environmental monitoring application

Abstract

Photodissociation of $CF_3Br$ at 234 nm The photodissociation dynamics of $CF_3Br$ in the A-band has been investigated utilizing a two-dimensional photofragment ion-imaging technique coupled with a state-selective resonance-enhanced multiphoton ionization scheme. The total translational energy distributions for the $Br(^2P_{3/2})$ and $Br^*(^2P_{1/2})$ channels are well characterized by Gaussian functions with average translational energies of 183 and 151 kJ/mol, respectively. The recoil anisotropies were measured to be β = 0.66 for Br and 1.83 for $Br^*$. It was found that $Br^*$ production is preferred, with a relative quantum yield of 0.80. The reduction in the recoil anisotropy for Br results from nonadiabatic coupling between the $^1Q_1$ and $^3Q_0$ states. The fraction of molecules that dissociate via a distorted pathway induced by symmetry reduction from $C_{3v}$ to $C_s$ is estimated to be 0.11. Photodissociation dynamics of $C_2H_4BrCl$ near 234 nm The $Br(^2P_j; j =1/2,3/2)$ atom formation of $C_2H_4BrCl$ was studied 234 nm. A two-dimensional photofragment ion-image technique coupled with a [2+1] resonant multiphoton ionization scheme was utilized to obtain speed and angular distributions of the nascent $Br(^2P_{3/2})$ and $Br^*(^2P_{1/2})$ atoms. The recoil anisotropy parameters for the Br and $Br^*$ production channels were measured to be β = 0.49 for Br and 1.55 for $Br^*$. The relative quantum yield for Br was found to be Φ (Br) + 0.67 ± 0.05, which favor Br. The probabilities of nonadiabatic transition from 3A´ to 4A´ surface and from 3A´ to 4A´ surface were found to be $P_{up} = 0.47$ and $P_{down} ＼leg 0.91$, respectively. The nonadiabatic transition was discussed in the regime of $C_s$ symmetry. Photodissociation dynamics of $C_6H_5Br$ and $C_6F_5Br$ near 234 nm Photodissociation dynamics of $C_6H_5Br$ and $C_6F_5Br$ have been investigated at 234 nm using two-dimensional velocity mapping techniques. Trimodal translational energy distribu...