A direct digital synthesis chirped pulse Fourier transform microwave spectrometer

Area of Science:

• Physical Chemistry
• Spectroscopy
• Instrument Design

Background:

• Chirped pulse Fourier transform microwave (CP-FTMW) spectrometers offer high sensitivity, fast acquisition, and broad bandwidth for rotational spectra.
• Traditional CP-FTMW designs often involve bulky and power-intensive chirp generation components.

Purpose of the Study:

• To present the design and capabilities of a novel CP-FTMW spectrometer.
• To introduce direct digital synthesis (DDS) for chirped pulse generation in CP-FTMW spectroscopy.
• To evaluate the performance and suitability of DDS for in situ applications.

Main Methods:

• Construction of a new CP-FTMW spectrometer incorporating DDS for chirp generation.
• Extensive microwave characterization of the instrument.
• Deep averaging of the 10-14 GHz rotational spectrum of jet-cooled acetone.
• Utilized a high-speed digitizer with dedicated signal averaging electronics.

Main Results:

• The DDS-based chirp generation reduced size, weight, and power consumption by over an order of magnitude compared to traditional methods.
• The instrument achieved performance comparable to conventional designs.
• A data acquisition rate of 2.1 kHz was facilitated by the high-speed digitizer and averaging electronics.

Conclusions:

• Direct digital synthesis is a viable and advantageous method for chirp generation in CP-FTMW spectroscopy.
• The developed instrument is well-suited for in situ applications due to its reduced footprint and power requirements.
• The DDS-based CP-FTMW spectrometer demonstrates high performance and efficiency for acquiring rotational spectra.