2001/08/28 by C. W. Gardiner, Ashton S. Bradley, A. S. Bradley
Chemistry · Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Quantum, superfluid, helium dynamics #Spectroscopy and Laser Applications #cond-mat
paper · pdf · doi:10.1088/0953-4075/34/23/312
16 page J Phys B format plus 6 postscript figures
arxiv created 2001/08/28 · openalex publication_date 2001/11/23 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/04
We show that a correct formulation of the cold collision frequency shift for two photon spectroscopy of Bose-condensed and cold non-Bose-condensed hydrogen is consistent with experimental data. Our treatment includes transport and inhomogeneity into the theory of a non-condensed gas, which causes substantial changes in the cold collision frequency shift for the ordinary thermal gas, as a result of the very high frequency (3.9 kHz) of the transverse trap mode. For the condensed gas, we find substantial corrections arise from the inclusion of quasiparticles, whose number is very large because of the very low frequency (10.2 Hz) of the longitudinal trap mode. These two effects together account for the apparent absence of a `factor of two' between the two possibilities. Our treatment considers only the Doppler-free measurements, but could be extended to Doppler-sensitive measurements. For Bose-condensed hydrogen, we predict a characteristic `foot' extending into higher detunings than can arise from the condensate alone, as a result of a correct treatment of the statistics of thermal quasiparticles.