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Collision induced ultraviolet structure in nitrogen radar REMPI spectra
1Mechanical and Aerospace Engineering Department, Princeton University, Princeton, New Jersey 08544, USA.
The Journal of Chemical Physics
|January 3, 2015
Summary
Collision-induced interference in two-photon resonance-enhanced multiphoton ionization (2+2 REMPI) of nitrogen was observed. This interference, potentially from a 3+1 REMPI pathway, was suppressed using circularly polarized light for spectral analysis.
Area of Science:
- Atomic and Molecular Physics
- Laser Spectroscopy
- Chemical Physics
Background:
- Resonance-enhanced multiphoton ionization (REMPI) is a sensitive technique for studying molecular species.
- Understanding interference effects is crucial for accurate spectral analysis in molecular nitrogen (N2).
Purpose of the Study:
- To investigate interference phenomena in 2+2 REMPI of N2 under atmospheric conditions.
- To identify the source of observed spectral interference and explore methods for its suppression.
Main Methods:
- Performed 2+2 resonance-enhanced multiphoton ionization (REMPI) measurements in molecular nitrogen.
- Utilized circularly polarized light to suppress spectral interference.
- Analyzed the resulting spectra to understand the underlying processes.
Main Results:
- Observed significant interference in the (1,0) vibrational band of the N2 a(1)Πg ← X(1)Σg(+) electronic manifold.
- Interference was suppressed using circularly polarized light, enabling rotational analysis.
- The interference was found to be collision-induced, varying with gas composition, temperature, and pressure.
Conclusions:
- Hypothesize that the interference originates from a 3+1 REMPI process via the a(″1)Σg(+) electronic state.
- Circularly polarized light effectively mitigates interference, facilitating detailed spectral studies.
- Collision-induced processes significantly impact REMPI spectra of N2.
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