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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.

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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.