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
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Masters Course: Experimental Techniques Detection of molecular species (with lasers) Techniques Direct absorption techniques Cavity Ring Down Cavity Enhanced.
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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