[2] [2] Bell W E, Bloom A L, Lynch J. Rev. Sci. Instum., 1961, 32: 688.

[3] [3] Brewer R G. Rev. Sci. Instum., 1961, 32: 1356.

[4] [4] Vanier Jacques, Audion Claude. The Quantum Physics of Atomic Frequency Standards Adam Hilger, 1989, 1: 1271.

[5] [5] Volk C H, Frueholz R P. J. Appl. Phys., 1985, 57(3)： 980.

[7] [7] Camparo J C, Mackay R. Journal of Applied Physics, 2007, 101: 053303.

[8] [8] Fukuyo H, Iga K I. Japanese Journal of Applied Physics, 1970, 9(7): 729.

[10] [10] Luna F R T, Cavalcanti G H, Coutinho L H, et al. Journal of Quantitative Spectroscopy & Radiative Transfer, 2002, 75： 559.

[11] [11] Fukuyo H, Iga K I, Kuramochi N, et al. Japanese Journal of Applied Physics, 1970, 9: 729.

[12] [12] Vanier J, Bernier L G. IEEE Transactions on Instrumentation and Measurement IM-30, 1981. 277.

[13] [13] Tako Toshiharu, Koga Yasuki, Hirano Isao. Japanese Journal of Applied Physics, 1975, 14(5); 949.

[14] [14] Moe G, Tam A C, Happer W. Physical Review A, 1976, 14(1): 349.

[15] [15] Todd Dass, Gerald Freed, John Petzinger, et al. GPS Clocks in Space: Current Performance and Plans for the Future. 34th Annual Precise Time and Time Interval (PTTI)Meeting, Reston, VA, USA, December 03-05, 2002, 175.