Features of the Excitation of Principal Series Lines of Atoms of the Zinc Subgroup by an Electron Impact: I. Cadmium

Abstract

Using the technique of intersecting beams of slow electrons and atoms of zinc, excitation functions of four spectral lines of Zn I principal series corresponding to the 4snp $${}^{1}P_{1}^{^\circ }$$ → 4s2 1S0 transitions for n = 4, 5, 6, and 7 are measured. Their wavelengths are 213.9, 158.9, 145.8, and 140.4 nm, respectively. Within the energy range of 11–18 eV, the effect of postcollision interaction of electrons (slow scattered and fast ejected ones) has been revealed on these functions with the decay of the autoionizing state. At incident electron energies of ∼11–13 and ∼15–18 eV, such interaction leads to an additional population of the initial levels for these lines and, correspondingly, to the formation of maximum on their excitation functions due to the capture of a scattered electron into these excited levels. The terms of atomic autoionizing states responsible for the observed maximums are determined. The combined influence of the decay of these autoionizing states and postcollision interaction is expressed in the energy shift of the maximums on the excitation functions relative to positions of the corresponding autoionizing states. Using a straightforward calculation in the classical approximation, effective widths of the electron decay of the autoionizing states are estimated. The estimates involve an exact formula and approximation formulas. The latter are valid for different relations between the value of the postcollision shift of maximums on the excitation functions and electron bonding energy at the atomic level. They are used for the determination of effective widths when approximating experimental shifts by the least squares method.