Infrared transitions and oscillator strengths of Ca and Mg

Aims. While solar spectra contain a lot of Ca I and Mg I infrared (IR) lines, no laboratory-measured spectra of these atoms have been reported for wavenumbers below 2000 cm-1. This study reports Ca I spectra in the 1300–4500 cm-1 range and Mg I spectra in the 1300–4500 cm-1 range. Methods. We performed a time-resolved Fourier transform infrared spectroscopy study of a plasma created by the laser ablation of MgF2 and CaF2 targets in a vacuum. The oscillator strengths (f-values) were calculated using quantum defect theory (QDT), which shows good agreement with the available experimental and theoretical results. Results. We report several Ca I and Mg I IR lines that have not been measured previously in laboratory. The recorded spectra allow the excitation energies of some Ca I and Mg I states with high orbital momentum (l = 4,5) to be determined. We also provide a long list of QDT-calculated f-values for Ca I and Mg I in the range of 800–9000 cm-1.