Unlocking synchrotron sources for THz spectroscopy at sub-MHz resolution.

Area of Science:

• Molecular Spectroscopy
• Terahertz (THz) Science
• Spectrometer Development

Background:

• Synchrotron radiation (SR) is crucial for terahertz (THz) molecular spectroscopy due to its brightness and broadband nature.
• Current SR-based measurements are limited to ~30 MHz resolution by Fourier-transform infrared spectroscopy (FTIR).
• Observing fine spectral features requires higher resolution, particularly for internal molecular dynamics and angular momentum couplings.

Purpose of the Study:

• To develop a novel spectrometer for enhanced resolution in THz molecular spectroscopy.
• To achieve sub-MHz resolution using SR and a THz molecular laser.
• To enable Doppler-limited spectroscopy across a wide THz frequency range.

Main Methods:

• Development of a spectrometer utilizing heterodyne mixing.
• Integration of SR with a newly available THz molecular laser (1-5.5 THz).
• Demonstration of THz comb mixing with the molecular laser.

Main Results:

• Achieved a spectral resolution of 80 kHz, a significant improvement over previous methods.
• Enabled sub-MHz, Doppler-limited spectroscopy across the 1-5.5 THz range.
• Demonstrated the potential for precise molecular transition frequency determination.

Conclusions:

• The developed spectrometer is the first SR-based instrument capable of sub-MHz resolution in the THz region.
• This advancement allows for the observation of closely spaced spectral features.
• Future applications include highly precise molecular frequency measurements using THz combs.