Ultrasonic Investigation of the Acceptor Ground State of Si(B) I. The Longitudinal and Transverse Relaxation Rates of the Strain‐Split Two‐Level System

The “spin”‐lattice relaxation of the two‐level system of the strain‐split acceptor ground state of Si(B) is determined from the temperature dependence of the ultrasonic relaxation attenuation, around 10 K. It is found that Raman relaxation alone does not fit the results but that, in addition, an Arrhenius‐type of relaxation, possibly due to a Jahn‐Teller effect, is involved. The transverse relaxation is obtained from intensity‐dependent and hole‐burning measurements of the resonant attenuation. At small acceptor concentrations it is determined by “spin”‐lattice relaxation alone; for higher concentrations an additional temperature‐independent interaction term is found much smaller than expected for elastic dipole or exchange interaction.