The photolytic cage effect of iodine in gases and liquids

Abstract

The photolytic cage effect is studied over a wide density range of several bath gases in the laser flash photolysis of iodine at 694.3 nm. Particular attention is paid to measurements in the ‘‘simple’’ solvents Xe and Kr, which are compared with molecular dynamics calculations. Measurements in polyatomic gases and liquids are also reported, as well as the variation of the cage effect with temperature and applied magnetic field. While measuring the cage effect under such a wide variety of conditions, we simultaneously obtain the second order rate constants for iodine atom combination, which help to establish the detailed mechanism of this elementary chemical reaction.

Quantum Yields for the Photodissociation of Iodine in Compressed Liquids and Supercritical Fluids

“…Even at the highest densities the photodissociation quantum yield is still around 25%. Slightly higher quantum yields were found in xenon at 323 K by van den Bergh and co-workers [8,9] after excitation to the A or A state at a wavelength of 694 nm (open triangles).…”

“…Subsequent quantitative investigations of the cage effect by Noyes were aimed at understanding the dependence of iodine dissociation quantum yields on the wavelength of the excitation light and solvent viscosity [2][3][4]. In systematic studies over wide density ranges Troe and co-workers [5,6] and van den Bergh and co-workers [7][8][9] found quantum yields smaller than unity at surprisingly low gas pressures, namely, one or two orders of magnitude below liquid densities. Similar results were obtained with excitation at 694 nm and 581 nm, i.e.…”

“…Photodissociation quantum yields of iodine in xenon ( : λ exc = 532 nm at 313 K, this work; : λ exc = 694 nm at 323 K[8,9]; • : in krypton with λ exc = 694 nm at 298 K (density scaled)[5]). The experimental data are compared with MD simulations of iodine in xenon ( --: excitation to the 1 Π u state (R = 0.55 nm); · · · · ·· : excitation to the 1 Π u state (upper curve: R = 0.45 nm, lower curve: R = 0.65 nm); ------: excitation to the A state; : excitation to the 1 Π u state[19]; • : excitation in the ground state[18]).…”

ArI 2 (X)→Ar+I 2 (B) photodissociation: Comparison between linear and T-shaped isomers dynamics

“…In this context, the iodine molecule has been extensively studied under a wide variety of experimental conditions in gases, liquids and matrices. [1][2][3][4][5][6][7][8][9][10][11][12] The van der Waals ͑vdW͒ clusters in which several atoms or molecules are bound to a chromophore provide ideal model systems to investigate photofragmentation and relaxation processes affected by these weak intermolecular interactions, [13][14][15][16][17][18][19] bridging the gap between gas-phase isolated molecules and molecules solvated in liquids and cryogenic matrices. These complexes can be studied with the use of supersonic beams, and a large number of experimental and theoretical studies have been devoted to the study of the excitation and decay of vdW complexes involving I 2 .…”

A three-dimensional wave packet study of Ar⋅ ⋅ ⋅I2(B )→Ar + I + I electronic predissociation

“…In this context, the iodine molecule has been studied extensively under a wide variety of experimental conditions in compressed gases and liquids. [1][2][3][4][5][6][7][8][9] It has been suggested that some of the dynamical processes observed in gases and condensed phases could actually be due to the formation of van der Waals complexes between I 2 and the solvent particles. These complexes can be studied with the use of supersonic beams, and a large number of experimental and theoretical studies have been devoted to the study of the excitation and decay of van der Waals complexes involving I 2 .…”