A294666 Decimal expansion of the hyperfine transition of neutral hydrogen in Hertz.

1, 4, 2, 0, 4, 0, 5, 7, 5, 1, 7, 6

Offset

10,2

Comments

The value is most often quoted as 1420405751.768 +- 0.02. Is it certain that the second digit after the decimal point is a 6? (Astonishingly enough, the most precise measurement seems to date back to 1970... Is it even sure that they used the relatively new definition of the second (from 1967) and that the later redefinition of the speed of light (resp. meter), needed to convert wavelengths to frequency, has no influence on the last digits?) - M. F. Hasler, Jun 17 2025

References

Ludwig Bergmann, Clemens Schaefer (edited by Wilhelm Raith), Constituents of Matter: Atoms, Molecules, Nuclei, and Particles, Walter de Gruyter & Co., Berlin, 1997, p. 203.

Links

Table of n, a(n) for n=10..21.

Helmut Hellwig et al., Measurement of the Unperturbed Hydrogen Hyperfine Transition Frequency, IEEE Transactions on Instrumentation and Measurement, vol. IM-19, No. 4 (1970), pp. 200-209.

Wikipedia, Hydrogen line

Wikipedia, Primeval Structure Telescope

Formula

Equals E * A081823 / A003676, where E is the energy (in eV) emitted after spin-flip transition of atomic hydrogen in its ground electronic state, and A081823 and A003676 are the elementary charge e = 1.602176634*10^-19 C and Planck's constant h = 6.62607015*10^-34 Js, both exact values by definition of the SI system.

Example

1420405751.7667 +- 0.0009 Hz.

Crossrefs

Cf. A003676 (Planck's constant h), A081823 (elementary charge e).

Sequence in context: A182501 A048819 A076114 * A051478 A121829 A021708

Adjacent sequences: A294663 A294664 A294665 * A294667 A294668 A294669

Keyword

nonn,cons,less

Author

Arkadiusz Wesolowski, Nov 06 2017

Status

approved