A random-walk model for spectral relaxation of trapped electrons in alcohols

✍ Scribed by K. Funabashi; W.H. Hamill

• Publisher: Elsevier Science
• Year: 1978
• Tongue: English
• Weight: 288 KB
• Volume: 56
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(78)80214-0

✦ Synopsis

Following pulsed irradiation of disordered solids, optical absorption of trapped electrons decays in the far red and increases in the visible. The random-walk model of Scher and Control, quantitatively apphcable to electron mobility by timeof-flight, supports hopping to successively deeper traps. Baxendale and Wardman 111 measured the optical spectra of solvated electrons, e;, in several liquid alcohols near their melting points following pulsed irradia-tions_ The initial near-infrared absorbance A of trapped electrons, e;,decayed within 1 ws, accompanied by growth of e;in the visible. Baxendale and Sharpe [2] found for ethanol and propanol at 77 K that the presence of =102 M benzyl chloride greatly reduced growth of ecin the visible spectrum, and only slightly increased the decay rate in the far red. They concluded that the conversion e; + e; involves trap-to-trap hopping. These authors subsequently found [3] that decay the red and growth in the visible are fnst order at 2 1 I8 K in l-propanol, with k = exp [-812/(T-73.5)]. Below 118 K the kinetics are not first order. The changes extend to >l s, are temperature dependent, but they are orders of magnitude faster than those calculated from the preceding equation. They proposed that electron transport occurs by thermal excitation from the initial traps and capture by successively deeper traps. Electron transport becomes progressively slower, and A is roughly linear in log (time). There is a considerable loss of oscillator strength.