Horiba Scientific FluoroMax-4 Operation Manual page 224

® ®
FluoroMax -4 & FluoroMax -4P with USB rev. D (30 Jul 2012)
tion
P
Polarization ( )
Pulse-sampling method
Quantum yield (Fluo-
rescence quantum
yield)
Quenching
Raman scattering
Rayleigh scattering
Real Time Control
which discrete current pulses from the tube are integrated and "counted
up". With this method, noise inherent to the detector can be minimized,
resulting in much more sensitive detection than used in traditional cur-
rent- or voltage-detection modules. A limit to photon-counting is when
pulse pileup occurs, that is, when two counts occur too fast for the
module to count them individually. This creates nonlinearity in the de-
tector at high signal-levels.
A measurement of the fluorescence polarization of a sample defined as
the linear polarizer's component's intensity divided by the natural light
intensity. The measurement of polarization provides insight into mo-
lecular size, shape, and the environment surrounding the molecule.
Another unit, called millipolarization (mP), is used to monitor small
changes in polarization. P = mP × 1000.
A technique for measuring fluorescence lifetimes, in which an initial
population of fluorophores is excited by infinitely short pulses of light.
An advantage of this technique is the direct recording of time-resolved
emission spectra.
The efficiency of the absorption of a photon to be emitted (fluoresced).
Quantum yields typically are expressed as percents. The fluorescence
quantum yield is the percentage of photons absorbed that actually leads
to fluorescence. This number is reduced by scattering, quenching, in-
ternal conversion, and non-radiative effects, along with several other
specialized processes. Measurements of quantum yields usually require
the comparison of a sample with a known fluorophore such as
Rhodamine-B or Ru(BPY)
Reduction in the fluorescence intensity of a sample by a variety of
chemical or environmental influences. Quenching may be static, dy-
namic, or collisional in nature.
Scattering caused by vibrational and rotational transitions. Raman
bands generally appear red-shifted relative to the incident electromag-
netic radiation. The primary characteristic of Raman scatter is that the
difference in energy between the Raman peak and the incident radia-
tion is constant in energy units (cm
Light scattering from particles whose dimensions are much smaller
than the wavelength of incident light. Rayleigh-scattered light is of the
same energy as the incident light. The scattered radiation's intensity is
inversely proportional to the 4
radiation.
The FluorEssence™ software application that gives the user full con-
trol of the system in real-time, in order to optimize the system setup for
a particular measurement. Use Real Time Control to find the optimal
slit widths for sample measurements, or to check that the excitation
.
3
–1
).
th
power of the wavelength of incident
13-8
Glossary