[1] Ramsey N F 1985 Molecular Beams (Oxford: Oxford
University)

[2]Riehle F 2004 Frequency Standards (Basics and
Applications) (Weinheim: WILEY-VCH Verlag GmbH and Co.KGaA)

[3]Morinaga A et al 1989 Appl. Phys. B {\bf 48 165

[4]Zibrov A S et al 1994 Appl. Phys. B {\bf 59 327

[5]Eberly J H, Narozhny N B and Sanchez-Mondragon J J 1980
Phys. Rev. Lett. {\bf 44 1323

[6]Narozhny N B, Sanchez-Mondragon J J and Eberly J H 1981
Phys. Rev. A {\bf 23 236

[7]Scully M O and Zubairy M S 1997 Quantum Optics (Cambridge:
Cambridge University) p p 197 201 202

[8]Rempe G and Walther H 1987 Phys. Rev. Lett. {\bf 58
353

[9]An K and Feld M S 1997 Phys. Rev. A {\bf 56 1662

[10]Wang Y Q et al 1986 The Principle of Quantum
Frequency Standard (Beijing: Science Press) (in Chinese)

[11]Li B and Chen J B 2009 Chin. Phys. Lett. {\bf 26
123203

[12]Hang K K et al 2006 Chin. Phys. Lett. {\bf 23 3198

[13]Yang D H and Wang Y Q 1991 Opt. Commun. {\bf 85 319

[14]Wang Z C 2003 Thermodynamics and Statistical Physics
3rd edn (Beijing: Higher Education Press) (in Chinese)