TY - JOUR
T1 - Spin-orbit relaxation and recombination dynamics in I-2(CO2)n and I-2(OCS)n cluster ions
T2 - A new type of photofragment caging reaction
AU - Sanov, Andrei
AU - Sanford, Todd
AU - Nandi, Sreela
AU - Lineberger, W. Carl
PY - 1999/7/8
Y1 - 1999/7/8
N2 - We report a new type of photofragment caging reaction that is only possible because of the strong solvent-induced perturbation of the inherent electronic structure of the chromophore. The photoexcitation of I-2 at 395 nm promotes it to a dissociative state correlating with I-+I*(2P1/2), the only near-ultraviolet dissociation channel for unsolvated I-2. In I-2 (CO2)n and I-2(OCS)n clusters, interaction with the solvent is observed to result in extremely fast spin-orbit relaxation. In general, we detect three reaction pathways: (1) direct dissociation of the chromophore to I-+I*(2P1/2); (2) the I-2→I-+I* dissociation, followed by spin-orbit quenching leading to I-+I(2P3/2) products; and (3) the I-2→I-+I* dissociation, followed by spin-orbit quenching and I-+I(2P3/2)→I-2 recombination and vibrational relaxation. We present experimental evidence of the spin-orbit relaxation and caging and discuss possible mechanisms. The results include: the measured translational energy release in 395 nm photodissociation of unsolvated I-2, indicating that solvation-free dissociation proceeds exclusively via the I-I* channel; ionic product distributions in the photodissociation of size-selected I-2(CO2)n and I-2(OCS)n clusters at the same wavelength, indicating the above three reaction channels; and ultrafast pump-probe measurements of absorption recovery, indicating picosecond time scales of the caging reaction. We rule out the mechanisms of spin-orbit quenching relying on I*-solvent interactions without explicitly considering the perturbed electronic structure of I-2. Instead, as described by Delaney et al. (companion paper), the spin-orbit relaxation occurs by electron transfer from I- to I*(2P1/2), giving I(2P3/2)+I-. The 0.93 eV gap between the initial and final states in this transition is bridged by differential solvation due to solvent asymmetry. Favorable comparison of our experimental results and the theoretical simulations of Delaney et al. yield confidence in the mechanism and provide understanding of the role of cluster structure in spin-orbit relaxation and recombination dynamics.
AB - We report a new type of photofragment caging reaction that is only possible because of the strong solvent-induced perturbation of the inherent electronic structure of the chromophore. The photoexcitation of I-2 at 395 nm promotes it to a dissociative state correlating with I-+I*(2P1/2), the only near-ultraviolet dissociation channel for unsolvated I-2. In I-2 (CO2)n and I-2(OCS)n clusters, interaction with the solvent is observed to result in extremely fast spin-orbit relaxation. In general, we detect three reaction pathways: (1) direct dissociation of the chromophore to I-+I*(2P1/2); (2) the I-2→I-+I* dissociation, followed by spin-orbit quenching leading to I-+I(2P3/2) products; and (3) the I-2→I-+I* dissociation, followed by spin-orbit quenching and I-+I(2P3/2)→I-2 recombination and vibrational relaxation. We present experimental evidence of the spin-orbit relaxation and caging and discuss possible mechanisms. The results include: the measured translational energy release in 395 nm photodissociation of unsolvated I-2, indicating that solvation-free dissociation proceeds exclusively via the I-I* channel; ionic product distributions in the photodissociation of size-selected I-2(CO2)n and I-2(OCS)n clusters at the same wavelength, indicating the above three reaction channels; and ultrafast pump-probe measurements of absorption recovery, indicating picosecond time scales of the caging reaction. We rule out the mechanisms of spin-orbit quenching relying on I*-solvent interactions without explicitly considering the perturbed electronic structure of I-2. Instead, as described by Delaney et al. (companion paper), the spin-orbit relaxation occurs by electron transfer from I- to I*(2P1/2), giving I(2P3/2)+I-. The 0.93 eV gap between the initial and final states in this transition is bridged by differential solvation due to solvent asymmetry. Favorable comparison of our experimental results and the theoretical simulations of Delaney et al. yield confidence in the mechanism and provide understanding of the role of cluster structure in spin-orbit relaxation and recombination dynamics.
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U2 - 10.1063/1.479346
DO - 10.1063/1.479346
M3 - Article
AN - SCOPUS:0000927676
SN - 0021-9606
VL - 111
SP - 664
EP - 675
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 2
ER -