Elsevier

Chemical Physics

Volume 4, Issue 1, April 1974, Pages 133-141
Chemical Physics

Mössbauer spectra of the tetrakis-(1,8-naphthyridine) iron(II)perchlorate in external magnetic fields. Evidence of slow relaxation ln paramagnetic iron(II)

https://doi.org/10.1016/0301-0104(74)80053-4Get rights and content

Abstract

57Fe Mössbauer spectra of [FeL4] (ClO4)2 where L = 1,8-naphthyridine have been measured at 4.2°K in external magnetic fields up to 55 kG parallel to the direction of the γ-rays. The spectra have been fitted in the spin hamiltonian approximation assuming an orbital singlet ground state of the 5D multiplet of Fe2+. The fit of the spectra is not unique, yet the possible spin hamiltonian parameter sets found lead to a spin doublet ground state split by less than 1 cm−1. The transition probabilities for spin-lattice relaxation have been calculated for those ground states. Orbach processes via excited spin hamiltonian states cannot be neglected. The results explain the fluctuations observed in the spectra in low external magnetic fields (10 kG).

The spin hamiltonian parameters provide information on the orbital energy levels. Therefrom the reduction of the quadrupole splitting by spin—orbit coupling results to be small thus explaining the extremely large quadrupole splitting of 4.54 mm/sec.

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