Spatial emission distribution of YO, Y I, Y II and Y III radiation in an inductively coupled plasma for the elucidation of excitation mechanisms

Abstract

Vertical and radial emission profiles of radiation from yttrium monoxide (YO), atom (Y I), singly charged ion (Y II) and doubly charged ion (Y III) were measured precisely and compared with the emission pattern observed when a highly-concentrated yttrium solution was injected into the ICP. By comparing the obtained spatial emission pronies, experimental evidence has been found that argon ions contribute to excite high-level Y II lines from the atom ground state in a one-step process. The spatial profile of the excitation temperature derived from low- and high-level Y II lines reveals that charge transfer excitation occurs at off-axis positions in the initial radiation zone (IRZ), and the excitation by electron collisions is dominant in the normal analytical zone (NAZ). It is confirmed that the ICP is close to local thermal equilibrium (LTE) in the NAZ if the argon ionization temperature derived from the electron number density is used as LTE temperature.