Wavelength-selective bleaching (''burning holes'') in the optical spectra of trapped electrons in organic glasses

This paper presents experimental evidence confirming that the broad optical absorption spectra of trapped electrons in glassy 3-methylpentane and methyltetrahydrofuran (MTHF) are convolutions of spectra of electrons trapped with different energies. Laser light of wavelengths near or to the red of the et− optical absorption maximum selectively depopulates electrons which absorb at the bleaching wavelength, thus creating a hole in the et− spectrum. Some additional indications as to the spectral properties of the individual electrons are given by the observations that (1) illumination of et− produced in MTHF at 25°K with laser light to the blue of the absorption maximum results in nearly uniform bleaching throughout the spectrum; (2) et− produced in MTHF at 67°K and illuminated at 25°K with 1064 nm are bleached less efficiently then et− produced at 25°K and have a low probability of being shifted to traps typical of mobile electron trapping at 25°K; (3) the spectra of et− in MTHF are progressively red-shifted as the temperature at which they are produced is lowered from 97 to 10°K, and the resolution of the peaks observable in the spectrum produced at 72°K is lower for spectra of et− produced at higher (97°K) or lower (25 and 10°K) temperatures. Some implications of these observations are discussed.