Resonance-enhanced multiphoton ionization for diagnosis of a weakly ionized plasma
We describe an experimental setup in which resonance-enhanced multiphoton ionization (REMPI) is used for diagnosis of neutral particles (atoms or molecules) effusing from a plasma. Quantum-state-specific detection, achieved by selective ionization with the help of REMPI, yields the distribution over their internal degrees of freedom. Discrimination against nonlaser-produced ions is performed by means of the combination of an electric and a magnetic field. The applicability of the setup is demonstrated by the determination of the rotational temperature of ground-state hydrogen molecules in a multicusp ion source. Under nondischarge conditions a detection limit is achieved of approx. =2 x 10/sup 10/ state-selected hydrogen molecules/cm/sup 3/, corresponding to a value of approx. =7 x 10/sup 8//cm/sup 3/ at the analysis region. Under discharge conditions, this detection limit is deteriorated by the presence of metastable hydrogen molecules, which are ionized in a one-photon process.
- Research Organization:
- Association EURATOM-FOM, FOM-Institute for Atomic and Molecular Physics, Kruislaan 407, NL-1098 SJ Amsterdam, The Netherlands
- OSTI ID:
- 6460214
- Journal Information:
- Rev. Sci. Instrum.; (United States), Vol. 58:8
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ION SOURCES
PLASMA DIAGNOSTICS
ION BEAMS
MASS SPECTROMETERS
DEGREES OF FREEDOM
ELECTRIC FIELDS
GROUND STATES
HYDROGEN IONS
MAGNETIC FIELDS
METASTABLE STATES
MULTI-PHOTON PROCESSES
PHOTOIONIZATION
PLASMA DENSITY
BEAMS
CHARGED PARTICLES
ENERGY LEVELS
EXCITED STATES
IONIZATION
IONS
MEASURING INSTRUMENTS
SPECTROMETERS
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