The optical absorption spectrum of Ni2+ ion doped in lecontite (sodium ammonium sulphate dihydrate) single crystal has been studied at room and liquid air temperatures. All the bands could be assigned assumingOh symmetry for the Ni2+ ion in the crystal. The splitting of3T1g (F) band at liquid air temperature has been attributed to spin-orbit interaction. The crystal field and spin-orbit parameters derived areDq=1000 cm−1;B=740 cm−1;C/B=4.27 and ζ=600 cm−1. All the bands observed show a blue shift when the crystal was cooled to liquid air temperature.
