ters Course: Experimental Techniques Detection of molecular species (with lasers) Techniques Direct absorption techniques Cavity Ring Down Cavity Enhanced Ionization detection (multi-photon) Laser-induced fluorescence Photo-acoustic technique Nonlinear optical techniques Optogalvanic technique Issues Resolution Spectroscopy vs quantitative Pressure Color (excitation level) Quantum state selectivity
Detection of molecular species (with lasers). Issues Resolution Spectroscopy vs quantitative Pressure Color (excitation level) Quantum state selectivity. Techniques Direct absorption techniques Cavity Ring Down Cavity Enhanced Ionization detection (multi-photon) - PowerPoint PPT Presentation
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Masters Course: Experimental Techniques
Detection of molecular species (with lasers)
Techniques
Direct absorption techniquesCavity Ring DownCavity Enhanced
Ionization detection (multi-photon)
Laser-induced fluorescence
Photo-acoustic technique
Nonlinear optical techniques
Optogalvanic technique
Issues
Resolution
Spectroscopy vs quantitative
Pressure
Color (excitation level)
Quantum state selectivity
Masters Course: Experimental Techniques
Direct absorption
Beer’s law, Beer-Lambert law
nlII exp0
Exponent cross section in [cm2]
n density in [cm-3]
l absorption length in [cm]
nl column density in [cm-2]
Problem:- Measuring against a non-zero baseline
Masters Course: Experimental Techniques
Photo-acoustic detection
RT-VT relaxation
Kinetic energy= acoustics
Use of acoustic resonator
Phase sensitive detectionAcoustic modulation
Masters Course: Experimental Techniques
Optogalvanic detection
Principle: change the resistance over a plasma dischargeby resonantly exciting atoms/molecules