Hyperfine Zeeman effects in Pr3+:LaCl3using the fluorescence line-narrowing technique

New fluorescence line-narrowing experiments carried out on the 6011 AA line of Pr 3+ in LaCl 3 show evidence of a temperature-dependent process of relaxation between hyperfine states of the excited level 1 D 2 A 1 . Frequency distribution of the additional lines due to this relaxation leads to a determination of the second-order Zeeman hyperfine interaction. A detailed discussion of the small spectroscopic effects arising ( approximately=10 -3 cm -1 ) on the levels under study is also presented.