Doppler-free Spectroscopy of Buffer-Gas-Cooled Calcium Monohydroxide.

Area of Science:

• Molecular Spectroscopy
• Laser Cooling
• Physical Chemistry

Background:

• Buffer-gas cooling is a technique used to prepare molecules in a cold, slow state for high-resolution spectroscopy.
• Calcium hydroxide (CaOH) is a unique polyatomic molecule that can be laser-cooled and trapped, making it a target for advanced spectroscopic studies.
• Previous Doppler-limited spectroscopies had limitations in resolving fine spectral features of molecules like CaOH.

Purpose of the Study:

• To perform Doppler-free spectroscopy on buffer-gas-cooled CaOH molecules.
• To resolve previously unresolved low-J Q1 and R12 transitions.
• To demonstrate the applicability of buffer-gas cooling for high-resolution spectroscopy of polyatomic radicals.

Main Methods:

• Utilized buffer-gas cooling to prepare CaOH molecules.
• Employed Doppler-free spectroscopy techniques to obtain high-resolution spectra.
• Calibrated spectral frequencies using Doppler-free iodine spectra for high accuracy.

Main Results:

• Observed and reported five Doppler-free spectra of CaOH, including low-J Q1 and R12 transitions.
• Achieved spectral frequency accuracy below 10 MHz.
• Determined the ground-state spin-rotation constant, showing excellent agreement (within 1 MHz) with millimeter-wave data.

Conclusions:

• Successfully demonstrated Doppler-free spectroscopy on a polyatomic radical (CaOH) using buffer-gas cooling.
• The high precision achieved validates the effectiveness of the buffer-gas cooling method for molecular spectroscopy.
• This work provides crucial high-resolution spectroscopic data for advancing laser cooling schemes for polyatomic molecules.