Untitled - IRS

262 GLOSSAR
MALDI Matrix assisted laser desorption ionization. MALDI is used for the investigation of delicate
substances (e.g. large biomolecules) by ’soft ionization’. The substance is embedded into
an organic matrix. The laser desorbes material from the surface and during the vaporization
process the molecules are ionized. Subsequently the ions are mass-analyzed in a mass
spectrometer. (Eq. (1.0)) [p. 13]
MASER Device that produces and amplifies electromagnetic radiation mainly in the microwave
region of the spectrum. The name is an acronym derived from ’microwave (or molecular)
amplification by stimulated emission of radiation’. The first maser used a beam of ammonia
molecules that passed along the axis of a cylindrical cage of metal rods, with alternate
rods having positive and negative electric charge. The nonuniform electric field from the
rods sorted out the excited from the unexcited molecules, focusing the excited molecules
through a small hole into the resonator. The output was less than one microwatt (10 −6 W)
of power. (Eq. (1.0)) [p. 5]
MPI cross-section Cross-section for multiphoton ionisation. Symbol µm. The product of MPI-crosssection
times the m-th power of the → power density I m gives the ionisation rate (per
unit time). Therefore the unit of the MPI cross-section is length 2m power −m time −1 (e.g.
µm 2m W −m s −1 ). (Eq. (7.12)) [p. 201]
Offener Resonator Open resonator. Resonator with reflecting surfaces only at both ends along beam
propagation and not along the sides parallel to the beam. (Eq. (2.56)) [p. 30]
Optische Dichte Optical density. Product of optical thickness and molar absorption coefficient
kM (Eq. (8.25)) [p. 217]
Optische Dicke Optical thickness. Product of (molar) concentration and absorption
length (Eq. (8.25)) [p. 217]
Optisches Pumpen optical pumping. The use of light energy to raise the atoms of a system from one
energy level to another. A system may consist of atoms having random individual magnetic
spin quantum numbers. When optically pumped, the atoms will undergo a realignment of
individual magnetic spins with respect to the direction of the light beam; that is, there will
be a rearrangement of magnetic energy levels. (Eq. (1.0)) [p. 6]
Parität Parity A wavefunction that changes its sign by inversion of the space coordinates has odd
(negative) parity. A wavefunction which is symmetric with respect to the origin does not
change its sign under space inversion and has even (positive) parity. (Eq. (4.18)) [p. 98]
PCS(1) Photon correlation spectroscopy. PCS is used for the determination of particle size (i.e.
hydrodynamic diameter) of particles in suspension. Particles move into the beam of a cw
laser due to their Brownian motion and scatter light which is detected by a photon counter.
The larger the particle is, the more slowly is its diffusion and hence the longer it stays in
the laser beam and scatters photons. The time one particle scatters photons is obtained by
calculating the so called self-correlation function of the photon-counter current. From this
function the particle size is obtained. (Eq. (1.0)) [p. 13]
PCS(2) By PCS, the zeta potential (particle charge) can be measured. An electric field is applied
and particles experience a force which is proportional to their charge. Superimposed on