Single-crystal rotational data of CW-EPR and two-pulse fieldthrough deprotonation to the NH 2 form of the two coordiswept ESE collected at room and low temperatures lead to the nated glycine NH 3 groups. A similar mechanism of Cu 2/ spin-Hamiltonian parameters g z Å 2.2596, g y Å 2.0647, g x Å 2.0529, charge compensation was proposed for the TGS crystal (7). A z Å 151.2 1 10 04 cm 01 , A y Å 2.5 1 10 04 cm 01 , and A x Å 42.2 Only a few papers report results of pulsed EPR studies 1 10 04 cm 01 which are temperature independent. The parameters of TGS crystals, whereas TGSe has been not studied by and Cu 2/ ion site in the crystal unit cell are very similar to those this technique so far. A characteristic feature of the electron in the triglycine sulfate crystal. Electron-spin-echo measurements spin echo in TGS:Cu 2/ is a very pronounced and regular of the spin-lattice relaxation time T 1 in the temperature range modulation pattern of the echo-decay envelope as reported 4.2-90 K gave identical results for inversion-and saturation-reby Schweiger ( 8 ). Vo ¨lkel et al. have studied anomalies of covery methods, indicating a negligible spectral-diffusion contrithe electron spin -lattice relaxation time T 1 and elecbution. The T 1 decreases from 275 ms at 15 K to 1.7 ms at 83 K and the temperature dependence is governed by the direct (one-tron phase memory time T M of the glycine radical phonon) process at low temperatures and two-phonon Raman NH / 3 C g HCOO 0 in the vicinity of the ferroelectric phase process at higher temperatures. A new analytical form of the I 8 transition of the TGS crystal (9, 10 ) . They found that the transport integral of the Raman term is proposed. The best fit to relaxation rate 1 / T 1 is a quadratic function of temperature the theoretical expression was found for the Debye temperature in the range 100 -350 K. This is characteristic for the two-Q D Å 168 { 3 K which is comparable to Q D Å 171 K calculated phonon Raman relaxation process above the Debye temperfrom the elastic constants of the crystal. ᭧ 1996 Academic Press, Inc.
ature. In such a case, one can expect that there exists a chance to determine the Debye temperature from the relaxation data collected in the lower temperature range, espe-This work was supported by the Polish Scientific Research Committee lattice relaxation rate. Such a method has been previously under Project KBN-2 P03B 038 08. The authors gratefully acknowledge used for crystals with a low concentration of paramagnetic the help of Professor M. Drozdowski, Technical University of Poznan, for his discussion on the elastic constants of the crystal and calculations of the ions (19, 22, 23). The accuracy of the Q D determination is acoustic-wave velocity.
relatively high when T 1 data are collected from low temperatures up to T ú Q D . With limited accuracy, Q D can be