Magneto-Optical Studies of Excited States of the Cl Donor in CdS

We have studied the $2s$ and $2p$ levels of the Cl donor in CdS by two methods: first, by observing "two-electron transitions" in which an exciton bound to the neutral donor Cl decays, leaving the donor in its $n=2\mathrm{}$ excited states; second, by observing Raman-scattering transitions between the $n=1\mathrm{}$ and $n=2\mathrm{}$ donor levels. We have accurately measured the positions of the $2p_x$, $2p_z$, and $2s$ levels relative to the $1s$ state to be 24.36 ± 0.02, 24.19 ± 0.02, and 23.88 ± 0.02 meV; the anisotropy factor $\alpha =0.054\mathrm{}\pm 0.005$; and the electron mass $m_{\perp }=0.190\mathrm{}\pm 0.002$. With less precision, we have measured $m_{\parallel }=0.180\mathrm{}\pm 0.010$ and estimated the donor binding energy to be 32.7 ± 0.4 meV.