Recoil-Free Resonant Absorption of 35.3-keV Gamma Rays of Te¹²⁵ and Hyperfine Structure of Absorption Spectrum

With the source of Sb 125 embedded in copper or iron metal, the recoilfree resonant absorption of 35.3-kev gamma rays by Te 125 atoms in the crystals of tellurium, α-TeO 2 , MnTe, and CrTe cooled with liquid nitrogen has been studied. For the crystals of tellurium and α-TeO 2 , large quadrupole splittings are observed. The values of | e 2 q Q |=1.6×10 -6 eV, or | e 2 q Q / h |=400 Mc are obtained for both the crystals of tellurium and α-TeO 2 , and the quadrupole moment of the first excited state of Te 125 is estimated to be about 0.2 barn under some assumptions. For the crystal of MnTe and the source embedded in copper, a simple Lorentz line is observed and from the half width the half life of the 35.3-keV level of Te 125 is calculated to be (1.8±0.3)×10 -9 sec. For the crystal of CrTe, line broadening due to the internal magnetic field is observed. The internal field in the CrTe crystal is evaluated to be about 50 Koe. With the source embedded in iron metal, Zeeman splittings are observed, although they are poorly resolved. The magnetic moment of the first excited state of Te 125 and the internal magnetic field at the Te nuclei in the iron environment are estimated to be about 0.7 n.m. and 600 koe respectively.