Line identification of atomic and ionic spectra of Holmium in the near infrared spectral range from 700 nm to 1750 nm

Abstract

The aim of the study is to extend the list of spectral lines of atomic and single ionized holmium (Ho) into the near infrared wavelength range up to 1750 nm. Spectra of a Ho hollow cathode discharge lamp with neon or argon as buffer gases have been measured with a Fourier Transform spectrometer in different spectral ranges. In total, the range from 700 nm to 1750 nm i.e. from $5710{\mathrm{cm}}^{-1}$ to $14280{\mathrm{cm}}^{-1}$ has been covered. A total of almost 800 spectral lines were detected. Based on the known energy levels of atom and ion Ho, 589 lines could be classified as Ho I transitions and 31 lines as Ho II transitions. The remaining 171 lines could mostly be classified as different Ho I or Ho II, based on different signal-to-noise ratios in spectra measured with different buffer gases. In the wavelength range from 1200 nm to 1750 nm, a list of Ho lines is presented for the first time. In the wavelength range from 700 nm to 1200 nm 216 lines had not been listed in literature up to now.