Title :
/sup 87/Rb versus /sup 133/Cs in cold atom fountains: a comparison
Author :
Sortais, Yvan ; Bize, Sebastien ; Nicolas, Christophe ; Santarelli, Giorgio ; Salomon, C. ; Clairon, A.
Author_Institution :
Lab. Primaire du Temps et des Frequences, Paris, France
Abstract :
We describe the operation of a laser cooled /sup 87/Rb frequency standard and present a new measurement of the /sup 87/Rb ground state hyperfine frequency with a relative accuracy of 2.4/spl times/10/sup -15/, by comparison with a Cs fountain primary standard. The measured frequency is 6 834 682 610.904 333(17) Hz. An evaluation of the frequency shift induced by cold collisions gives /spl Delta//spl nu///spl nu//sub Rb/=(-7.2/spl plusmn/20)/spl times/10/sup -24/ n~, where n~ is the average atomic density in cm/sup -3/. With our present 1 /spl sigma/ uncertainty of 10/sup -15/, this measurement is still compatible with 0 and about 300 times smaller than for /sup 133/Cs. We also report a test of a possible variation of the fine structure constant at the level of 2.7/spl times/10/sup -14/ yr/sup -1/, comparing Rb and Cs cold atom fountains.
Keywords :
Atomic clocks; Cesium; Fine structure; Frequency standards; Ground states; Hyperfine structure; Laser cooling; Rubidium; /sup 133/Cs; /sup 87/Rb; Cs; Rb; cold atom fountain; collisional shift; fine structure constant; frequency standard; ground state hyperfine splitting; laser cooling; Atom optics; Atomic beams; Atomic clocks; Atomic measurements; Charge carrier processes; Frequency; Masers; Phase noise; Stability; Testing;
Journal_Title :
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on
