Vacancy Relaxation in Cuprous Oxide (Cu$_{2-x}$O$_{1-y}$)
  Phonons are produced when an excited vacancy in cuprous oxide (Cu$_2$O) relaxes. Time resolved luminescence was used to find the excited copper vacancy (acceptor) and oxygen vacancy (donor) trap levels and lifetimes. It was also used to determine the typical energy and number of phonons in the phonon pulses emitted by vacancies. The vacancy properties of cuprous oxide are controlled by several synthesis parameters and by the temperature. We directly demonstrate the absorption of light by oxygen vacancies with transient absorption. Copper and oxygen vacancies behave differently, in part because the two kinds of traps capture carriers from different states. For example, the copper vacancy luminescence lifetime is around 25 times greater at low temperature. However, both kinds of vacancy luminescence are consistent with a Poissonian multiple phonon emission model. 
Laszlo Frazer, Kelvin B. Chang, Richard D. Schaller, Kenneth R.   Poepplemeier, John B. Ketterson
cond-mat.mtrl-sci