Search results
Results from the WOW.Com Content Network
A hydrogen maser, also known as hydrogen frequency standard, is a specific type of maser that uses the intrinsic properties of the hydrogen atom to serve as a precision frequency reference. Overview [ edit ]
A hydrogen maser. The hydrogen maser is used as an atomic frequency standard. Together with other kinds of atomic clocks, these help make up the International Atomic Time standard ("Temps Atomique International" or "TAI" in French). This is the international time scale coordinated by the International Bureau of Weights and Measures.
A hydrogen maser produces a very accurate signal (1.42 billion cycles per second), which is highly stable—to one part in a quadrillion (10 15). This is equivalent to a clock that drifts by less than two seconds every 100 million years. [5] A microwave signal derived from the maser frequency was transmitted to the ground throughout the mission.
Atomic clocks based on hydrogen standards are therefore regarded as secondary representations of the second. Hydrogen masers have superior short-term stability compared to other standards, but lower long-term accuracy. The long-term stability of hydrogen maser standards decreases because of changes in the cavity's properties over time.
For instance, in a hydrogen maser, the well-known 21cm wave transition in atomic hydrogen, where the lone electron flips its spin state from parallel to the nuclear spin to antiparallel, can be used to create a population inversion because the parallel state has a magnetic moment and the antiparallel state does not.
The black units in the foreground are Sigma-Tau MHM-2010 hydrogen maser standards. A master clock is a precision clock that provides timing signals to synchronise slave clocks as part of a clock network. Networks of electric clocks connected by wires to a precision master pendulum clock began to be used in institutions like factories, offices ...
A hydrogen atom with proton and electron spins aligned (top) undergoes a flip of the electron spin, resulting in emission of a photon with a 21 cm wavelength (bottom) The hydrogen line, 21 centimeter line, or H I line [a] is a spectral line that is created by a change in the energy state of solitary, electrically neutral hydrogen atoms.
1946 – Theodor V. Ionescu and Vasile Mihu report the construction of the first hydrogen maser by stimulated emission of radiation in molecular hydrogen. 1947 – Willis Lamb and Robert Retherford measure a small difference in energy between the energy levels 2 S 1/2 and 2 P 1/2 of the hydrogen atom, known as the Lamb shift.