Crossed-second-order effects in the isotope shift of the ground configuration 4f¹²6s²of Er I

Abstract

High-resolution laser-atomic-beam spectroscopy has been applied to study crossed-second-order effects in the isotope shift of the terms 4f126s2 3H and 3F of Er I. A parametric analysis of the cross second-order effects in the isotope shift 170-166Er has been performed. The J dependence of the isotope shift is interpreted through one parameter z4f with a coefficient having the same angular dependence as the spin-orbit interaction. Additional parameters T(SL) with angular coefficients equal to the square of the corresponding expansion coefficients of the wavefunctions are introduced to take account of term-dependent effects.