Frequency standards, metrology and fundamental constants

Hydrogenic systems, frequency standards and fundamental constants

“…As equation (4) shows, it may be expressed as a combination of five other fundamental constants: m e , e, h, c and e 0 . In fact, since 1983 the definition of the international system of units has been such that both c and e 0 have exact values, and so equation (4) relates the three constants m e , e and h. It is an important relationship in that it enables certain fundamental constants to be determined by more than one route (figure 2).…”

“…During the next decade, many improvements to the caesium atomic clock were developed, and it became clear that caesium atomic clocks could keep time with much greater stability than the Earth itself [4]. For this reason, in 1967 the 13th General Conference of Weights and Measures re-defined the SI unit of time, the second, as the duration of 9192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.…”

Editorial: Proceedings of the 2015 Workshop on the Determination of the Fundamental Constants

“…The 1973The , 1986The , 1998The , 2006, and 2010 CODATA updates were jointly published in Reviews of Modern Physics and the Journal of Physical and Chemical Reference Data, as will be the 2014 update (in preparation). 78,79 It is important to note the efforts by others who have worked both independently and in cooperation with the NRC and CODATA committees over the years to make recommendations and provide helpful discussions and debate over evaluation of the fundamental constants, including Gorbatesvich and coworkers (1967 and 1970), 80,81 Levyleblond (1977), 82 Pipkin and Ritter (1983), 83 Petley andcoworkers (1989 and2001), 84,85 Delaeter (1994), 86 Uzan (2003), 87 Conroy (2003), 88 and Karshenboim (2005 and2013). 89,90 …”