Spin polarization in a freely evolving sample of cold atoms

Analytical populations of a multilevel atom in a weak linearly-polarized light

“…However, exact populations can be obtained by using numerical coefficients rather than an analytical form. Since the method developed in this paper can be applied, regardless of the energy spacings, it would be more useful for atoms with relatively smaller excited-state energy spacings, such as 23 Na, 7 Li, or 39 K.…”

“…The former includes optical pumping [2], high-resolution laser spectroscopy [3], coherent population trapping (CPT) [4], and electromagnetic-induced transparency (EIT) [5], and the latter includes laser cooling and trapping of atoms, atom optics, and Bose-Einstein condensation of atoms [1]. Of these, optical pumping, which was studied before the introduction of the laser, is now widely used in atomic state preparation of interest [2,6,7]. While accurate analytical solutions can be obtained for twolevel atoms [8], numerical studies using the rate equations [9] or a density-matrix formalism [10,11] have been reported for multilevel atoms.…”

“…Extending previous studies, we report on the analytical calculation of populations under the influence of a weak polarized laser light, independent of the magnitude of the energy spacings of the excited state. After establishing the equations, although the calculation is applicable to other transitions with higher angular momentum quantum numbers, we restrict our calculation to the transitions F g = 1 → F e = 0, 1, 2 (F e = 1, 2) in the D 2 (D 1 ) line of an alkali-metal atom, such as 87 Rb, 23 Na, 7 Li, or 39 K, with a nuclear-spin angular momentum of I = 3/2 [1]. This is because the analytical calculation for other transitions is too difficult to handle analytically.…”

Preliminary Evaluation of the Cesium Fountain Primary Frequency Standard NMIJ-F2

“…A cryogenic sapphire oscillator (CSO) using a pulse-tube cryocooler [21], [22] is employed as the local oscillator to avoid the degradation of frequency stability due to the Dick effect [23], [24]. In spite of using neither a magneto-optical trap nor a cold-atomic-beamloaded optical molasses (OM) but a vapor-loaded OM, the use of high-power cooling laser and optical pumping (OP) to the Zeeman sublevel with m F = 0 [25] results in a high number of atoms involved in the Ramsey interrogation to improve the frequency stability. Due to the high frequency stability, some frequency shifts such as those due to the microwave power dependence and those due to collisions between cold atoms can be measured more precisely over shorter measurement times than previously.…”

Operation of NIM5 fountain with 1.5x10-15uncertainty and design of new NIM6 in NIM

“…A new cesium fountain clock NIM6 is under construction in the National Institute of Metrology China, and aiming to operate in 2016. Besides some improvements on the design of the Ramsey cavity to reduce the distributed cavity phase shift and microwave leakage, NIM6 is also aiming to collect more atoms from a MOT loading optical molasses (OM) and optical pumping [11,12], leading to a better signal to noise ratio at the detection. A new cryogenic sapphire oscillator (CSO) based frequency synthesizer [13] and ultra-stable microwave generated from ultra-stable laser are also under developing to reduce the microwave phase noise in order to reach the quantum projection noise, thus leading to a lower Type A uncertainty of the new fountain.…”