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Laser Flash Photolysis

Gilden Photonics FlashSENS system is a fully automated spectrometer for the measurement of transient absorption and emission lifetimes and spectra in the time range from nanoseconds to seconds. The system is supplied complete with Nd:YAG laser, digital storage oscilloscope, data acquisition, and analysis and presentation software. The system can obtain time-resolved absorption and luminescence lifetimes and spectra under full computer control.

Principle of Laser Flash Photolysis

The technique of flash photolysis has become an established method to study the photo-phsical and photochemical properties of compounds and materials under the effect of intense light.  It is  fully complimentary to luminescence spectral and lifetime fluorescence and phosphorescence measurements as measured in the FluoroSENS instrument.

The absorption of the sample is analysed using a Xenon lamp probe light that passes through the sample and is then measured using a photomultiplier detector or intensified time-gated CCD camera after it is analysed using either a monochromator or spectrograph respectively.  At the same time the sample is excited by using a short yet intense pulse of light from the laser.  This excitation light is normally incident to the sample at right angles to the probe light.  The transmission of the sample is measured before, during, and after the excitation light pulse is measured.  These transmission values reflect the change in the sample due to the excitation light and are often converted to a change in the optical density of the sample.  These changes are described by: 

ΔOD = (εT-εG)cL 

where:

  • εG is the extinction coefficient for the ground state,
  • εT is the extinction coefficient for the transient,
  • C is the concentration of transient species that has been converted from the ground state, and L is the optical path length.

Thus the principle of flash photolysis assumes that the transient state absorbs a different amount of light to the  ground state.  As a result two classifications of transient can occur:

Classification

Description

Transient Absorption: 

The excited state absorbs more light than during the ground state.

The photo-detector sees less light corresponding to the increased absorption level

Transient Depletion:

The excited state absorbs less light than the ground state.

The photo-detector sees more light corresponding to the decreased absorption level

The Laser Flash Photolysis experiment is essentially a time-resolved measurement of the change in absorption or the lifetime of the transient species concerned. FlashSENS operates in continuous mode with the probe lamp on all the time to ensure maximum lamp and hence probe stability.  Use of a steady state lamp means that the light levels in the probe beam can be at a reasonable level to minimise creation of the excited state and hence distortion of the measurement.  Thus it is more likely that the measurement represents the correct level of photo-products being generated.

Turning Precision Measurements Into High Quality Information

Applicable to solid, liquid and gaseous samples laser flash photolysis measurements are a unique method for studying the transient behavior of chemical and biological species, such as radicals, excited states, and other photo-excited intermediates, generated by an intense short pulse laser.

  SPECIFICATION
Optical Configuration Right angle geometry; optical accessories for other geometries including co axial and diffuse reflectance modes
Sensitivity Minimum ∆OD = 0.0005 (single shot)
Probe Source

150 W continuous Xenon arc lamp ozone free
200 - 2600 nm spectral range
XYZ bulb rear mirror and lamp focus adjustment User interchangeable xenon bulb

Laser Compact Nd: YAG, 1064, 532, 355, 266 nm output for other laser choices please consult GPL
Monochromator

Cerny-Turner design, 300 mm focal length, Triple-grating turret as standard with two gratings Standard Gratings: 1200 g/mm, 300 nm blaze and 1200 g/mm, 500 nm blaze
Wavelength accuracy ± 0.2nm, repeatability ±0.1nm
Bandpass 0.1 - 10nm continuously variable in steps of 0.05nm
Continuously variable precision knife-edge slits from 10μ to 3mm as standard
Stray light performance: 1 : 105

Detector High current photomultiplier 185 - 870nm, red sensitive photomultiplier Optiional InGaAs, InAs, InSb emission detectors for NIR measurements, and nanosecond time-gate intensified CCD system
Data Acquisition High speed Digital Storage Oscillocope, 2 GS/s
Software Measurement setup, method files, single and multiple kinetic measurement for transient absorption and emission studies. Time-resolved absorption spectra and time-resolved emission spectra, Full control of the wavelength and gratings selection, Pump laser flashlamp & Q-swith, Pump and probe high speed shutters as well as Oscilloscope trigger, Timebase, Voltage ranges and offsets
Power Requirements 90 - 260V ac, 50/60 Hz
Dimensions (D × W × H) 0.6m (D) × 0.83m (W) × 0.31m (H)
Certification CE marked
Computer Desktop or laptop USB 2.0 interface with Microsoft Windows® operating system
Laser Flash Photolysis
 

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Contact us

Gilden Photonics Ltd.
Unit 13 Telford Court
9 South Avenue
Clydebank Business Park
Glasgow G81 2NR
UK

tel: +44 (0)141 952 9475
fax: +44 (0)141 952 9400
sales@gildenphotonics.com