PHYS 26 |
| We have performed the first femtosecond near-infrared pump-probe experiments of equilibrated solvated electrons from liquid metal-ammonia solutions. The studies were carried out at electron concentrations of (2±1)E-4 mol/l corresponding to dilute solutions dominated by paramagnetic electrons with negligible spin-pairing. Using excitation pulses centered at 1280 nm, the dynamics were recorded for probe wavelengths ranging from 1200 and 2100 nm with a time resolution of roughly 100 fs. Immediately after photoexcitation, the absorption spectrum of the solvated electrons is strongly red-shifted with respect to their steady-state spectrum. Subsequently, a dynamic spectral blue-shift is observed that occurs with a time constant of (150±50) fs. A thorough analysis based on a dynamically evolving Kubo line-shape with a minimal number of fitting parameters demonstrates that these experiments can be understood either in terms of a simple temperature-jump model or in terms of a local density jump scenario. Non-adiabatic relaxation dynamics from the initially accessed “p-like” excited sate back to the “s-like” ground electronic state occur on a time scale faster than 100 fs. The results are compared with complementary experiments on the hydrated electron in aqueous bulk phases or on size-selected negative ion clusters. |
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Hydration: From Clusters to Aqueous Solution
8:20 AM-12:00 PM, Sunday, August 19, 2007 BCEC -- 159, Oral
Division of Physical Chemistry |