Rubidium oscillation

Rubidium oscillators ate the lowest priced members of the atomic oscillator family. They operate at 6,834,682,608 Hz, the resonance frequency of the mbid-ium atom ( Rb), and use the rubidium frequency to control the frequency of a quartz oscillator. A microwave signal derived from the ciystal oscillator is applied to the Rb vapor within a cell, forcing the atoms into a particn-lar energy state. An optical beam is then pnmped into the cell and is absorbed by the atoms as it forces them into a separate energy state. A photo cell detector measnres how much of the beam is absorbed and times a quartz oscillator to a frequency that maximizes the amount of light absorption. The qnartz oscillator is then locked to the resonance freqnency of rabidinm, and standard frequencies are derived and provided as outputs (Fig. 8). 

Rubidium oscillators continue to get smaller and less expensive, and offer perhaps the best price/performance ratio of any oscillator. Their long-term stability is much better than that of a quartz oscillator and they are also smaller, more reliable, and less expensive than cesium oscillators. 

The Q of a rubidium oscillator is about 10. The shifts in the resonance frequency are caused mainly by collisions of the rabidium atoms with other gas molecules. These shifts limit the long-term stability. Stability (cryX, at T = 1 sec) is typically 1 x 10 ", and about 1 x 10 at 1 day. The frequency offset of a rabidium oscillator ranges... 

Fig. 9.75 (a) Level diagram of the maser transition in rubidium. The transition frequencies are given in MHz. (b) Measured (points) and calculated (solid curve) Rabi oscillations of an atom in the cavity field at T = 0 K and at T = 3 K, damped by the statistical influence of the thermal radiation field. The experimental points were measured with a velocity selector that allowed transit times of 30-140 ps [1297, 1299]... 

Scientific Clocks. Scientific and industrial purposes demand atomic clocks with fer more accuracy and stabihty than that of household clocks or watches. Atomic clocks make use of the fact that all atoms are capable of existing at a number of different discrete (noncontinuous) levels of energy. As an atom jumps back and forth between a higher and a lower energy level, it resonates at a particular frequency, and this frequency is exactly the same for every atom of a given element. Eor example, cesium-133 atoms (one of the two types of atoms most commonly used in atomic clocks rubidium is the other) resonate between two particular energy levels at 9,192,631,770 cycles per second. (In fact, the time it takes for this number of oscillations of a cesium-133 atom to take... 

There are, however, striking differences in the effect of temperature on the oscillatory structure of S Q) and g(R). Compared with argon (Mikolaj and Pings, 1967), the higher-<2 oscillations in 5(2) for cesium (Fig. 3.11) and rubidium are much more strongly damped with increasing temperature. Near the critical point only a broad first maximum in 5(2) is seen for cesium and rubidium. 

Another experimental proof of the localization of cold atoms at the minima of a periodic optical potential was obtained by recording the resonance fluorescence spectra of cesium atoms trapped in three-dimensional optical molasses (Westbrook et al. 1990) and rubidium atoms in a one-dimensional optical potential (Jessen et al. 1992) The resonance fluorescence spectrum of a motionless two-level atom consists of the well-known Mollow triplet, which includes a central peak at the laser frequency u> and two side components displaced to the red and blue sides by an amount equal to the Rabi frequency (Mollow 1969). For a two-level atom oscillating in a potential well at a frequency lower than the Rabi frequency, each component of the Mollow triplet is split into side components corresponding to changes in the vibrational state of the atom. If the ratio between the oscillation amplitude of the atom in the potential well and the radiation wavelength (the Lamb-Dicke factor) is small, each component of the... 

Fig. 8.3 Density of a rubidium atomic gas at the center of a parabolic trap as a function of temperature. The total number of atoms was N = 10 , and the trap oscillation frequency was a>l2it= 16 Hz. (Adapted from CourteiUe et al. 2001.)...

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