Formation of a narrow group of intense lines in the photoexcitation and emission spectra corresponding to 3s23pN–(3s3pN+1 + 3s23pN−13d) transitions

Abstract

The strong mixing of the 3s3pN+1 and 3s23pN−13d configurations and its influence on the electric dipole transitions from/to the ground configuration 3s23pN have been considered in the isoelectronic sequences at the ionization degrees 5 ⩽ q ⩽ 35 and various numbers of electrons in the 3pN shell. It is shown that the redistribution of intensity from 3s–3p to 3p–3d transitions and its concentration in a narrow interval of wavelengths manifests itself in the photoexcitation and emission spectra for all isoelectronic sequences, but is more expressed for a half-filled and an almost-filled 3pN shell. It takes place at the condition that in the single-configuration approximation the energy levels of the 3s3pN+1 configuration, mainly populated by the photoexcitation from the ground level, are situated below such levels of the 3s23pN−13d configuration. This condition is fulfilled for the isoelectronic sequences up to q = 30; at larger ionization degrees such levels of both configurations begin to overlap and it causes the widening of the spectrum. For 3s23pN–3s23pN−13d transitions at N = 4 and 5 another reason for the narrowing of the spectrum is the existence of term groups formed by the Coulomb exchange interaction.