M�ssbauer spectroscopy with191,193Ir

Metal-insulator transition in the spinel-typeCuIr2(S1−xNagata1, Matsumoto2, Kato3 et al. 1998Phys. Rev. B

“…29,30 The source was always kept at 4.2 K while the absorber (ϳ100 mg Ir/cm 2 ) was maintained at temperatures between 4.2 and 150 K. The velocity calibration of the spectrometer was performed using a 57 Co/Rh source and a me- tallic iron absorber. The ␥ rays were counted with a highresolution Ge detector.…”

193Ir Mössbauer spectroscopy of Pt–IrO2 nanoparticle catalysts developed for detection and removal of carbon monoxide from air

“…Tetravalent iridium in crystalline IrO 2 is represented by a well-split doublet with IS = À0.84 mm/s and QS = 2.70 mm/s. It is also well established that metallic Ir and iridium in solid solution in Pt exhibit single lines, with QS = 0 mm/s and IS = À0.63 mm/s, respectively [15]. Fradin et al [16] showed that in binary Pt x Ir 1Àx alloys the isomer shift of 193 Ir varies linearly with x between two terminal values, as shown in Fig.…”

“…The quadrupole splitting of the 3/2 + ground state of 193 Ir nuclei reflects both the symmetry and covalence of the bonds between the iridium atoms and its ligands. Since the characteristic values of IS and QS are known for different oxidation states of iridium [15,16], one can determine from the measured IS and QS values the valence of iridium. However, one must remember that the s-electron density and the electric field gradient at Ir nuclei at the surface of very small particles can be modified as compared to the bulk solids, but the trends have these parameters change with the particle size have not yet been experimentally established.…”

“…The mass of 9Pt-1Ir catalyst samples needed for preparation of Mössbauer absorbers was typically 2-4 g. Usually, the absorbers contained only 10-20 mg Ir per cm 2 , which precludes any broadening of the absorption lines due to the absorber thickness saturation effect. The spectra were least-squares fitted with distribution of Lorentzian lines, and taking the 0.48 mm/s quadrupole splitting in the Os metal source [15] into account. All isomer shift values listed throughout this paper refer to Ir metal at À0.54 mm/s.…”

Electric Quadrupolar Contribution to the Nuclear Spin-Lattice Relaxation of Ir in Fe

“…To [20], g ͑193͒ 0.1061͑4͒ [21], and estimating the hyperfine anomaly with the help of the Moskowitz-Lombardi rule [22] and the ratio of the contact to the total hyperfine field [23].…”