Assignment of image excitation spectra of image in crystals using the simple model

The measured low-temperature image excitation spectra of image doped in crystals image, image and image [van Pieterson et al., Phys. Rev. B 65 (2002) 045113] are assigned and analyzed using the simple model proposed by Duan et al. [Phys. Rev. B 66 (2002) 155108] and Ning et al. [J. Alloy. Compd. 366 (2004) 34]. The agreement between theoretical and observed energies and intensities are acceptable, and at the same time the spectra are assigned in more detail.