Saturated spectroscopy is the method by which the exact energy of the
hyperfine transitions
In atomic physics, hyperfine structure is defined by small shifts in otherwise degenerate energy levels and the resulting splittings in those energy levels of atoms, molecules, and ions, due to electromagnetic multipole interaction between the nucl ...
within an atom can be found. When a monochromatic light is shone through an atom, the
absorption cross-section
Absorption cross section is a measure for the probability of an absorption process. More generally, the term cross section is used in physics to quantify the probability of a certain particle-particle interaction, e.g., scattering, electromagnet ...
is broadened due to
Doppler broadening
In atomic physics, Doppler broadening is broadening of spectral lines due to the Doppler effect caused by a distribution of velocities of atoms or molecules. Different velocities of the emitting (or absorbing) particles result in different Do ...
. Saturated spectroscopy allows the doppler broadened peak to be resolved so that the exact transitions can be found.
More than a decade after the first demonstration of
spectral hole burning
Spectral hole burning is the frequency-selective bleaching of the absorption spectrum of a material, which leads to an increased transmission (a "spectral hole") at the selected frequency.
Two basic requirements must be met for the phenomenon to ...
(or Lamb dip, a result of saturated absorption process) inside HeNe laser cavity at 1.1 μm in 1962, the greater majority of SA spectroscopy research was carried out with gas lasers and molecules in the mid-infrared.
But because SA requires high laser intensity, and the gas molecules usually have widely spread strong absorption spectra only in the mid-IR, while compact widely tunable mid-IR lasers were slow to develop, the SA technique has not been widely used for molecular chemical analysis besides precision metrology, which only been limited to the isolated wavelengths of HeNe and CO
2 lasers and limited number of molecules.
See also
*
Saturated absorption spectroscopy In experimental atomic physics, saturated absorption spectroscopy or Doppler-free spectroscopy is a set-up that enables the precise determination of the transition frequency of an atom between its ground state and an optically excited state. The ac ...
External links
Saturated Spectroscopyhole burning by Bennett
Spectroscopy
Scattering, absorption and radiative transfer (optics)
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