[1] [1] A. A. Kammskn; Laser Crystals: Their Physics and Properties, Springer-Verlag, Berlin Heidelberg, New York, 1981

[2] [2] B. R. Judd, Phys. Rev., 127, 750 (1962)

[3] [3] G. S. О felt, J. Chem. Phys., 37, 511(1962)

[4] [4] R. Re is feld and С. K. Jorgerson, Laser and Excited iSta fces of Hare Earths, 8pringer-Yerlag,Berlin Heidelberg, New York, 1977, p. 141

[5] [5] M. J. Weber, Phys. Rev., 157, 262(1967)

[6] [6] R. D. Peacock, Structure and Bonding, 22, 83(1975)

[7] [7] Su Qiang and Lu Yuhua, Rare Earths Sintroscopy, World Scientific, 1985, p. 379

[8] [8] Su Qiang et al., Kare Earths Spectroscopy,World Scientific, 1985, p. 385

[9] [9] Su Qiang et al., Chinese Physics-Lasers, 13(11),825(1986)

[10] [10] M. J. Weber and В. H. Matsinger, J. Chem. Phys., 57(1), 562(1972)

[11] [11] W. T. Car nail et al., J. Chem. Phys., 49 (10) 4412(1968)

[12] [12] B. Keller et al., Chem. Phys. Lett., 92 (5), 541(1982)

[13] [13] E. D. Peacock, J. Chem. Soc. Α., 2028(1971)

[14] [14] R. Reisfeld et al., Chem. Phys. Lett., 38, 188(1976)

[15] [15] J. A. Caird aDd L. G. DeShazer, IEEE J. Quant. Electr., QE-11, 97(1975)

[16] [16] J. A Caird, IEEE J. Quant. Electr., QE-11,874(1975)