Spectral Property and Stability of Color Centers in Alkali Halide Crystals Induced by He⁺ Ion Implantation at Room Temperature

Thin colored layers with high density defect centers could be produced on alkali halide crystals implanted by 300-400keV He⁺ ions at room temperature. Besides well known absorption bands, several new absorption bands and colloid absorption band are observed in the crystals, such as 520 and 842nm absorption bands in the implanted LiF crystals, 840nm absorption band in the implanted NaF :OH^- crystals, and 875 nm absorption band in the implanted NaC1:OH^- crystals.