Temperature and isotope effects on the shape of the optical absorption spectrum of solvated electrons in water

TLDR: In this article, the authors measured the optical absorption spectra of solvated electrons in H/sub 2/O and D/sub O and found that the spectrum at a given A/A/sub max/ shows a shift of +0.05 eV in the low-energy wing, reaching 0.03 eV at the absorption maximum.

Abstract: The optical absorption spectra of solvated electrons in H/sub 2/O and D/sub 2/O have been measured at 274, 298, 340, and 380 K. All the spectra were fitted very well with the Gaussian and Lorentzian shape functions at the low- and high-energy sides of the absorption maximum, respectively, excluding the high-energy tail. The spectrum does not shift uniformly with temperature. The temperature coefficient of absorption decreases rapidly with increasing energy on the low-energy side of the absorption maximum, while it changes only slightly on the high-energy side. When the temperature increases the Lorentzian width remains constant, the Gaussian width varies proportionally to T/sup 1/2/, and the spectrum becomes more symmetrical. On going from H/sub 2/O to D/sub 2/O we found that the spectrum at a given A/A/sub max/ shows a shift of +0.05 eV in the low-energy wing. The shift decreases with increasing energy, reaching 0.03 eV at the absorption maximum. On the high-energy side of the band the shift becomes negative at h..nu.. > 2.2 eV. The shift on the low-energy side seems to be related to the difference of the zero-point energies of the inter- and intramolecular vibrations. The wavelength dependence of the temperature and isotope effects ismore » consistent with the model that different types of excitation occur on the low- and high-energy sides of the absorption band. The temperature and isotopic dependence of the low-energy side are consistent with its width being due to phonon interactions.« less