Tunable diode laser spectrometer for pulsed supersonic jets: application to weakly-bound complexes and clusters

Area of Science:

• Molecular Spectroscopy
• Physical Chemistry
• Laser Science

Background:

• Studying weakly-bound molecular complexes requires sensitive spectroscopic techniques.
• Supersonic jet expansions are crucial for creating and isolating these complexes at low temperatures.

Purpose of the Study:

• To design and describe a novel apparatus for infrared spectroscopy of weakly-bound complexes.
• To demonstrate the apparatus's performance using specific molecular systems.

Main Methods:

• Utilizing a pulsed supersonic jet expansion probed by a tunable lead-salt (Pb-salt) diode laser spectrometer in rapid-scan mode.
• Employing a toroidal multi-pass mirror system for enhanced laser-molecule interaction (over 100 passes).
• Using both pinhole and slit nozzles to control rotational temperatures and spectral line sharpness.

Main Results:

• The apparatus successfully obtained infrared spectra of the van der Waals complex He-OCS.
• Spectra of seeded helium clusters, He(N)-OCS and He(N)-CO, were also acquired, showcasing the system's capability.
• A semi-automated wavenumber calibration procedure was implemented for accurate spectral analysis.

Conclusions:

• The developed apparatus is effective for high-resolution infrared spectroscopy of weakly-bound complexes.
• The system's design, featuring a multi-pass mirror and flexible nozzle options, enhances sensitivity and spectral quality.
• This work provides a valuable tool for investigating the structure and dynamics of van der Waals molecules and clusters.