**Optical Spectroscopy with
dispersive Spectrometers
Basics - Building Blocks - Systems - Applications**

**This page
summarizes chapter 4 of the book
"Applications of Dispersive Optical
Spectroscopy Systems",
ISBN 9781628413724, SPIE monographs, Bellingham, WA, USA **

**
Application – L2
Luminescence, dynamic
**
Lifetime
Measurement of

(Photo)Luminescence - Fluorescence – Phosphorescence

**This page
presents the directory, the signs and symbols, conversions, and equations
of the book, while the details are an exclusive part of the book**.

**L2.0 Introduction
**Photoluminescence phenomena are pump (excitation) and relaxation (emission)
processes. All of the excited states will return to the original, unexcited, state, quickly or
slowly. So called static luminescence is the equilibration between the two
sceneries. While the excitation light constantly pumps some electrons up to a higher state
of energy, some others return to the ground state, and emit light. The time span between excitation and the end of the emission has a spread, which
is defined by the chemical structure, the chemical environment, and thermal
situation of the sample. The emission starts quickly after excitation - but the
delay never is zero. While new electrons are pumped up, others already relax and emit light. Not
all electrons return from the excited state at the same time, they follow
an exponential relaxation function (e-function). The time between any point of
the decay curve (like the end of the excitation), and an emission level of 1/e (or 36.8 %) of the reference point is called
the LIFETIME. It may reach from the upper pico second range to hours or even
days.

The combination of all effects leads to an overlay of emission curves. A constructed example follows:

**L2.01 A look on the instrumentation available.
**There are two basic methods available and offered on the market: Pulsed and
modulated systems. Both methods can combine with polarization analysis, and with parallel wavelength detection.

L2.1 Pulsed methods

L2.1.1 The Synchrotron

L2.1.3 LED´s

**L2.2 Continuous Methods
L2.2.1 Phase Modulation
Analysis
**

The general equations for lifetime spectroscopy by phase/modulation are:

**For the calculation of the modulation factor, equation F42**

**F42: m = [ 1 + ** ** w ^{2}
*
t^{2}**

F is the resulting phase angle,

w is the circular frequency of modulation,

t is the lifetime,

m is the resulting modulation factor.

The behaviour of the two curves is next shown for a lifetime of 11 ns:

**L2.2.1.1 How does
a phase/modulation
system work?
**

**Graph L30 is the reproduction of a Phase-Modulation data representation, at a
lifetime of 11 ns**.

**L2.2.2 Multi Harmonic
Fourier Transform Systems (MHF)
**

**L2.3 Methods using parallel
Wavelength Detection
L2.3.1 Synchronized CCD
Gating
**

L2.3.2 Modulated MCP/CCD Analysis

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Spectroscopy with dispersive Spectrometers
Basics - Building Blocks - Systems - Applications " are reserved by
Wilfried **Neumann, D-88171 Weiler-Simmerberg.
Status April 2012**