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arXiv · 2506.07289

Imaging transient molecular configurations in UV-excited diiodomethane

Anbu Selvam Venkatachalam·Huynh Van Sa Lam·Surjendu Bhattacharyya·Balram Kaderiya·Enliang Wang·Yijue Ding·Loren Greenman·Artem Rudenko·Daniel Rolles
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Abstract

Femtosecond structural dynamics of diiodomethane ($\mathrm{CH_2I_2}$) triggered by ultraviolet (UV) photoabsorption at 290 nm and 330 nm are studied using time-resolved coincident Coulomb explosion imaging driven by a near-infrared probe pulse. We map the dominant single-photon process, the cleavage of the carbon-iodine bond producing rotationally excited $\mathrm{CH_2I}$ radical, identify the contributions of the three-body ($\mathrm{CH_2} + \mathrm{I} + \mathrm{I}$) dissociation and molecular iodine formation channels, which are primarily driven by the absorption of more than one UV photon, and demonstrate the existence of a weak reaction pathway involving the formation of short-lived transient species resembling iso-$\mathrm{CH_2I{-}I}$ geometries with a slightly shorter I-I separation compared to the ground-state $\mathrm{CH_2I_2}$. These transient molecular configurations, which can be separated from the other channels by applying a set of conditions on the correlated momenta of three ionic fragments, are formed within approximately 100 fs after the initial photoexcitation and decay within the next 100 fs.

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Anbu Selvam Venkatachalam, Huynh Van Sa Lam, Surjendu Bhattacharyya, Balram Kaderiya, Enliang Wang, Yijue Ding, Loren Greenman, Artem Rudenko, Daniel Rolles. 2026-02-04. Imaging transient molecular configurations in UV-excited diiodomethane. https://doi.org/10.1063/5.0284410

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