Temperature and density effects on the absorption maximum of solvated electrons in sub- and super-critical methanol

Yan, Y.*; Lin, M.; Katsumura, Yosuke*; Muroya, Yusa*; Yamashita, Shinichi; Hata, Kuniki ; Meesungnoen, J.*; Jay-Gerin, J.-P.*

The optical absorption spectra of the solvated electron (e) in sub- and super-critical methanol are measured by both electron pulse radiolysis and laser photolysis techniques, at temperatures in the range 220-270 C. Over the density range studied (0.45-0.59 g/cm), the position of the absorption maximum () of e is found to shift only slightly to the red with decreasing density. In agreement with our previous work in water, at a fixed pressure, decreases monotonically with increasing temperature in passing through the phase transition at (239.5 C). By contrast, at a fixed density, exhibits a minimum as the solvent passes above the critical point into the supercritical state. These behaviors are discussed in terms of microscopic arguments based on the changes that occur in the methanol properties and methanol structure in the sub- and supercritical regimes.