Untitled - IRS

GLOSSAR 261
Induzierte Emission Stimulated emission Prerequisite for laser action. In addition to spontaneous
photon emission an excited atom can be stimulated to emit a photon by the presence of a
second photon of exactly the excitation energy. The emitted photon has the same properties
as has the stimulating one, which results in monochromatic, coherent light. (Eq. (1.0)) [p. 5]
Inelastische Streuung Inelastic scattering. Scattering process where energy is transferred from the
photon to the scatterer (or vice versa) (Eq. (3.3)) [p. 44]
Interkombinationsverbot Prohibition of intercombination. Transitions between terms of different
multiplicity are forbidden. E.g. transitions from a singulet state to a triplet state can not
be caused by emission or absorption of a photon (Eq. (A.4)) [p. 238]
Kohärenz Coherence. When two beams of light can interact so as to produce interference fringes
the visibility of which is unity, they are said to be perfectly coherent. When their interaction
produces no fringes (but only photometric summation) they are said to be noncoherent or
incoherent. (Eq. (2.67)) [p. 36]
Kramers-Kronig Relation In the framework of the Drude model of electrons oscillating around an
atomic core, the Kramers-Kronig relation quantifies the complex refractive index, i.e. η, the
real index of refraction, andχ the imaginary part which corresponds to the absorptivity.
(Eq. (8.21)) [p. 216]
Laporte-Verbot Laporte-forbidden transitions ‘violate’ parity conservation. I.e. electric dipole transition
between states of equal parity. See also parity. (Eq. (4.18)) [p. 98]
Laser Induced Photoacoustic Spectroscopy See LPAS (Eq. (4.12)) [p. 93]
LIBD Laser Induced Breakdown Detection is a colloid detection method utilising plasma formation
in the high field of a focused laser beam. The size distribution of colloids between 5 nm and
1000 nm of mass concentration down to 10 −9 g dm −3 can be measured, often without sample
pretreatment, both, in the laboratory as well as in field experiments. (Eq. (1.0)) [p. 13]
LIBS Laser Induced Breakdown Spectroscopy. Technique used for the elemental analysis of solids,
liquids and gases. The sample is heated and vaporized by a the focused light of a pulsed laser.
During the cooling of the hot (ionised) gas recombination processes lead to the emission of
ionic and → atomic lines (c.f. atomic emission) which allow the quantitative determination
of element content. (Eq. (1.0)) [p. 13]
LIDAR Light Direction and Ranging (Eq. (1.0)) [p. 13]
LPAS Laser Induced Photoacoustic Spectroscopy. Matter which absorbs light is heated, expands
and causes an acoustic shock wave which can be detetected by a sensitive microphone. The
amplitude of the acoustic signal increases linearly proportionally with the concentration of
absorbers and with the molar absorptivity (or photon absorption cross-section respectively).
By scanning the excitation wavelength an optical absorption spectra is obtained, which in
turn is used to quantify the amount of species present in the sample. LPAS is applicable to
solids and liquids. The detection limit depends on the absorbtivity and is typically 1.5 orders
of magnitude lower than for UV-VIS detection. In contrast to UV-VIS, the measurement is
not disturbed by → scattering signals (e.g. due to colloids) since LPAS does not probe →
extinction but → absorption. (Eq. (4.12)) [p. 93]