Excited states and photodissociation dynamics of the triiodine radical (I3)

Abstract

The electronic spectroscopy and photodissociation dynamics of the I 3 radical are investigated with two experimental methods. The ground and several low-lying excited states of the I 3 radical are characterized by photoelectron spectroscopy of I 3Ϫ at 213 nm. Assignments of these states are discussed with reference to recent calculations. In addition, photodissociation of the I 3 radical was investigated at selected photon energies ͑4.59, 4.96, and 5.17 eV͒ by fast radical beam photofragment translational spectroscopy. Two product channels were observed with mass ratios of 1:2 and 1:1, and translational energy ( P(E T )) distributions were measured. The P(E T ) distributions for products with mass ratio 1:2 show that this channel corresponds to I 2 in various electronic states along with atomic I in its 2 P 3/2 or 2 P 1/2 state. The 1:1 channel corresponds primarily to concerted three-body dissociation to three I atoms.

Fast beam studies of I2− and I2−·Ar photodissociation

“…The photoproduct masses are found to be equal for the two-body events; therefore, the two-fragment images arise solely from events in which the iodine fragments are detected and the Ar atom either strikes the beam block or is not detected owing to less than unit efficiency. Similar events were seen in our previous studies of the photodissociation of I À 3 and I 3 [31,32]. In the three-fragment images, the Ar atoms have sufficient translational energy to travel past the beam block and appear as a bright spot in the center of the image.…”

Photodissociation of aqueous I3− observed with liquid-phase ultrafast mega-electron-volt electron diffraction

“…II); this generates the I 3 radical species, which has been observed in the gas phase to be marginally stable. 38 The quantum chemistry predicted difference in bond length between and I 3 would appear to be too small to generate an appreciable difference signal for this minority channel ( supplementary material Fig. S4), though secondary dissociation of I 3 could also be occurring in the experiment.…”

The electronic structure of the triiodide ion from relativistic correlated calculations: A comparison of different methodologies

“…We find a ground state with ⍀ =3/ 2 u , followed by states of ⍀ =1/ 2 g , 1/ 2 u , 3/ 2 g , and 1 / 2 g , respectively, in agreement with the experimental assignment. 33,34 The CASPT2 excitation energies are lower than those of IHFSCC͑b͒ by about 0.1-0.2 eV with the exception of the first excited state, which is higher for CASPT2. In this case, however, MRCI and IHFSCC are much more alike than for I 3 − , with discrepancies generally smaller than 0.1 eV.…”

“…III we compare the performance of the different methods in calculating excitation energies of I 3 − , both at selected bond lengths and at the equilibrium geometries for the symmetric configuration. We also take the opportunity to discuss results for the triiodide radical ͑I 3 ͒, a species that was experimentally observed in photoionization studies involving I 3 − in the gas-phase, 33,34 and that was also investigated theoretically by Kosloff and co-workers. Finally, in Sec.…”