A230458 Decimal expansion of Δν_{Cs} in unit s^{-1}; one of the seven units of the 2019 SI system.

9, 1, 9, 2, 6, 3, 1, 7, 7, 0

Offset: 10

Author

N. J. A. Sloane, Oct 19 2013

Keywords

• nonn
• cons
• fini
• full

Comments

The second s is defined to be exactly 9192631770 periods of the resonance frequency of the hyperfine transition of the cesium 133 atom.

Prime factors of this number are 2^1, 3^2, 5^1, 7^2, 47^1, 44351^1. - John W. Nicholson, Jun 15 2014

The value was fixed in 1968 by the 13th CGPM in terms of periods of the radiation due to the transition between the two hyperfine levels of the ground state of 133Cs atoms. - Stanislav Sykora, Mar 30 2015

In the 2019 SI system of units (see the BIPM link, and A322415) one of the seven units is Δν_{Cs} = Δν(^{133}Cs){hfs} = 9192631770 s^{-1}. - _Wolfdieter Lang, Feb 12 2019

Examples

			c = 9192631770 m/s.
		

Links

• BIPM, On the revision of the International System of Units (SI), BIPM, Nov 13-16 2018.
• Bureau International des Poids et Mesures, Unit of time (second)
• W. M. Itano and N. F. Ramsey, Accurate measurement of time, Scientific American, 269 (July 1993), 56-65.
• N. F. Ramsey, Precise measurement of time, American Scientist, 76 (No. 1, 1988), 42-49.
• Wikipedia, Second
• Wikipedia, 2019 redefinition of SI base units

Crossrefs

Cf. A003678 (c), A003676 (h), A081823 (e), A070063 (k), A322578 (N_A), A244823, A322415.

Programs

Mathematica

IntegerDigits@ 9192631770 (* Michael De Vlieger, Mar 30 2015 *)

Formula

Δν_{Cs} = 9192631770 s^{-1}.