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  2. Hydrogen maser - Wikipedia

    en.wikipedia.org/wiki/Hydrogen_maser

    A hydrogen maser, also known as hydrogen frequency standard, ... This cavity is tuned to the 1.420 GHz resonance frequency of the atoms. [4]

  3. Hydrogen line - Wikipedia

    en.wikipedia.org/wiki/Hydrogen_line

    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.

  4. Atomic clock - Wikipedia

    en.wikipedia.org/wiki/Atomic_clock

    The rack mounted units in the background are HP 5071A cesium beam clocks. The black units in the foreground are Sigma-Tau MHM-2010 hydrogen maser standards. An atomic clock is a clock that measures time by monitoring the resonant frequency of atoms.

  5. Lyman-alpha - Wikipedia

    en.wikipedia.org/wiki/Lyman-alpha

    Lyman-alpha, typically denoted by Ly-α, is a spectral line of hydrogen (or, more generally, of any one-electron atom) in the Lyman series.It is emitted when the atomic electron transitions from an n = 2 orbital to the ground state (n = 1), where n is the principal quantum number.

  6. Nuclear magnetic resonance spectroscopy - Wikipedia

    en.wikipedia.org/wiki/Nuclear_magnetic_resonance...

    The resonant frequency, energy of the radiation absorbed, and the intensity of the signal are proportional to the strength of the magnetic field. For example, in a 21-tesla magnetic field, hydrogen nuclei resonate at 900 MHz. It is common to refer to a 21 T magnet as a 900 MHz magnet, since hydrogen is the most common nucleus detected.

  7. Molecular vibration - Wikipedia

    en.wikipedia.org/wiki/Molecular_vibration

    A molecular vibration is a periodic motion of the atoms of a molecule relative to each other, such that the center of mass of the molecule remains unchanged. The typical vibrational frequencies range from less than 10 13 Hz to approximately 10 14 Hz, corresponding to wavenumbers of approximately 300 to 3000 cm −1 and wavelengths of approximately 30 to 3 μm.

  8. Proton nuclear magnetic resonance - Wikipedia

    en.wikipedia.org/wiki/Proton_nuclear_magnetic...

    Proton nuclear magnetic resonance (proton NMR, hydrogen-1 NMR, or 1 H NMR) is the application of nuclear magnetic resonance in NMR spectroscopy with respect to hydrogen-1 nuclei within the molecules of a substance, in order to determine the structure of its molecules. [1]

  9. Hydrogen atom - Wikipedia

    en.wikipedia.org/wiki/Hydrogen_atom

    A hydrogen atom is an atom of the ... like nuclear reactors and Nuclear Magnetic Resonance ... of quantum states radiates light at a frequency of the cosine. ...