Absolute measurements of the frequency of an He—Ne/CH4 standard over a decade

Measurements carried out on a laser multiplication chain at the All-Russia Scientific-Research Institute of Physicotechnical and Radio Engineering Measurements made it possible to improve the precision of determination of the frequencies of laser standards recommended for reproducing the unit of length. This investigation showed that the long-term drift of the dimensionless combination of the atomic constants g₁α²(m_e/m_p)^1/2 did not exceed 10^–12 per year (g₁ is the gyromagnetic ratio of the proton, α is the fine-structure constant, and m_e and m_p are the masses of an electron and a proton).