Electron bubbles, small-polaron holes, and charge-induced effects in solid deuterium

The charge-induced absorption spectrum in the fundamental band of solid ${\mathrm{D}}_2$ under proton-beam irradiation has been measured. Under higher spectral resolution than for previous work, we examine the spectra for both normal and ortho-enriched samples. Timing experiments are presented in which the growth and decay of these spectral features are monitored following onset and termination of beam irradiation, and both spectra and timing as a function of temperature are examined. These experimental results are then interpreted within a model in which electron bubbles and small-polaron holes figure prominently. That at least two different kinds of both positive and negative charge carriers are needed to explain the results seems certain. The identification of the positive molecular-ion species is uncertain but evidence for the probable formation of ${\mathrm{D}}_9$ ${\mathrm{}}^{+}$ is presented. The consequences for charge transport are critically examined.