  Photoluminescence and thermally stimulated luminescence of synthetic and
natural (morion and smoky) $\alpha$-quartz crystals doped with aluminum and
alkali ions were studied. The photoluminescence spectrum is characterized with
the main blue band around 400 nm (~ 3.1 eV). The corresponding luminescence
center is based on a defect containing aluminum and alkali as compensators in
natural and synthetic quartz crystals. Photoluminescence can be detected at
high temperatures above 700 K. The thermal quenching activation energy is 0.15
eV and the frequency factor is 3 10$^7$ s$^{-1}$. In the samples with silver
ions the main luminescence band is located at ~ 260 nm (~ 4.7 eV) with a time
constant of ~ 37 $\mu$s at 80 K, and in the samples with copper ions the PL
band is at ~ 360 nm (~ 3.4 eV) with a time constant ~ 50 {\mu}s at 80 K. For
luminescence associated with silver the energy of thermal quenching is 0.7 eV
with a frequency coefficient of 1 10$^{14}$ s$^{-1}$, and for the luminescence
related to copper, these parameters are 0.55 eV and 10$^{14}$ s$^{-1}$. The
differences in intra-center luminescence properties of the same defect
containing alkali ions or noble ions are based on differences in electronic
transitions. In the case of alkali ions the charge transfer transitions between
oxygen and alkali ions. In the case of noble ions absorption-luminescence
corresponds to intra ion transitions. Radiation properties are related to
trapping of an electron on one valence ion. Created atom moves out of aluminum
containing defect. The hole remains on aluminum-oxygen defect. Thermally
stimulated luminescence is related to release of atom, it diffusion to aluminum
defect with the hole on oxygen and following radiative recombination.
