An isolated line-shape model based on the Keilson and Storer function for velocity changes. I. Theoretical approaches

Area of Science:

• Spectroscopy
• Atomic and Molecular Physics
• Quantum Chemistry

Background:

• Modeling spectral line shapes is crucial for understanding molecular interactions.
• Existing models often simplify the complex interplay between Doppler, collisional, and confinement effects.
• The speed dependence of collisional parameters and Dicke narrowing require sophisticated theoretical treatment.

Purpose of the Study:

• To develop and validate new models for isolated spectral line shapes.
• To incorporate the effects of confinement (Dicke narrowing) and speed-dependent collisional parameters.
• To provide accurate predictions for spectral line shapes across different regimes.

Main Methods:

• Classical description of the autocorrelation function of the optical transition moment.
• Keilson and Storer model for radiator translational velocity changes.
• Numerical solution of differential equations using discretized velocity grids.
• Projection onto generalized Laguerre polynomials and spherical harmonics.

Main Results:

• Two distinct modeling approaches yield identical results.
• The models accurately reproduce experimental linewidth measurements for pure H(2) Q(1) Raman line.
• Satisfactory agreement with measured linewidths at various densities was achieved.

Conclusions:

• The developed models effectively capture complex line shape phenomena.
• The approach is validated by experimental data for hydrogen gas.
• This work provides a robust framework for future spectroscopic studies.