J. Phys. Colloques
Volume 37, Numéro C6, Décembre 1976International Conference on the Applications of the Mössbauer Effect / Conférence Internationale sur les Applications de l'Effet Mössbauer
|Page(s)||C6-917 - C6-917|
J. Phys. Colloques 37 (1976) C6-917-C6-917
HYPERFINE INTERACTION AND LIFETIME OF ANOMALOUS SPIN STATES OF IRON (II) IN [57 Co(phen)3] (ClO4)2.2H2O BY TIME-DEPENDENT MÖSSBAUER EMISSION SPECTROSCOPYR. GRIMM1, P. GÜTLICH1, R. LINK1 and E. KANKELEIT2
1 Institut für Anorganische Chemie und Analytische Chemie der Unversität, D 6500 Mainz/BRD
2 Institut für Kernphysik der Technischen Hochschule Darmstadt, D 6100 Darmstadt/BRD
Using the time-differential Mössbauer coincidence technique we have measured emission-spectra of [57Co(phen)3] (ClO4)2.H2O (phen = 1, 10 -phenanthroline) as the source in the temperature range 4.2-80 K. The lifetimes of the anomalous high spin states of 57Fe(II) originating from the EC process of 57Co in the source matrix have been derived. The two spin quintet (S = 2) states of iron (II) decay into the singlet (S = O) state of [57Fe(phen)3] (ClO4)2.2H2O, which is the only observable species in the corresponding absorption experiment at any temperature. Using the computer code of Hoy et al.  we have evaluated the intensities of the high spin (IHS) and low spin (ILS) quadrupole doublets by a least squares fitting procedure, taking into account the effect of time filtering, absorber thickness and source broadening as well as the cosine smearing effect. The intensity ratio of the high spin to low spin states IHS/ILS is derived as a function of time after the decay of the 57Co nucleus. Evaluating the intensity ratio [MATH] by means of a least squares fitting procedure we obtain the lifetimes π of the excited states as a function of temperature (TA, TE : time window ; P0, γ : initial population probability and decay constant of the unstable state respectively ; 2 π0 : experimental time resolution ; f : Debye-Waller factor). For the ratio of the DW factors we obtained the value fHS/fLS = 1.The results are discussed on the basis of the recombination of a positive charge hole at the ligands-formed by radiolysis with an electron. At lower temperatures long range tunneling should be the dominant process.