Intermediate state polarization in multiphoton ionization of HCl

Area of Science:

• Molecular spectroscopy
• Quantum chemistry
• Photochemistry

Background:

• Resonance enhanced multiphoton ionization (REMPI) is a powerful technique for probing molecular excited states.
• Understanding intermediate state polarization and photofragment angular distributions is crucial for interpreting REMPI experiments.
• Previous studies have explored these phenomena, but a comprehensive theoretical and experimental framework is needed.

Purpose of the Study:

• To provide a detailed theoretical description of intermediate state polarization and photofragment angular distribution in REMPI.
• To experimentally investigate these effects in the E(1)Sigma(+) and V(1)Sigma(+) states of HCl.
• To characterize intermediate state polarization using a universal parameter 'b' and validate theoretical predictions with experimental data.

Main Methods:

• Theoretical modeling of intermediate state polarization and photofragment angular distributions.
• Two-photon transitions populating the E(1)Sigma(+) and V(1)Sigma(+) states of HCl.
• Resonance enhanced multiphoton ionization (REMPI) absorption spectroscopy.
• Three-dimensional ion imaging detection following REMPI.

Main Results:

• The universal parameter 'b' characterizes intermediate state polarization and contains information on two-photon excitation symmetry and phase shifts.
• Photofragment angular distributions are a product of intermediate state spatial distribution and fragment distribution from an unpolarized state.
• Experimental results for HCl indicate a predominantly perpendicular two-photon transition.
• Experimentally obtained H(+) ion fragment angular distributions agree well with theoretical predictions.

Conclusions:

• The developed theoretical framework accurately describes intermediate state polarization and photofragment angular distributions in REMPI.
• Experimental validation using HCl demonstrates the utility of the parameter 'b' in characterizing molecular photoionization dynamics.
• This work provides a foundation for advanced studies of molecular photodissociation and ionization processes.