Isomer Shift ofFe57in Transition Metals under Pressure

Abstract

Isomer shifts of ${\mathrm{Fe}}^{57}$ in several transition metals have been measured as a function of pressure up to nearly 300 kbar. The host metals studied were Cr, Co, Ni, Nb, Mo, Pd, Ta, W, Pt, and Au. The data are discussed in terms of the volume dependence of (1) the density at the nucleus from $4s$-like conduction electrons and (2) the density at the nucleus from $3s$ core electrons which are shielded by the $3d$-like conduction electrons. Results of the previous paper regarding amount of $4s$ character, $n_s$, and amount of $3d$ character, $n_d$, on the iron impurity atom, are used. The data are shown to be consistent with (1) $n_s$ decreasing or $n_d$ increasing, or both, as one goes through each transition-metal series toward more $d$ electrons of the host, and (2) $n_s$ decreasing or $n_d$ increasing, or both, as pressure is applied to the host metal. The degree of the effect (2) is shown to be related to the calibration constant of the isomer shift.