APPARATUS AND TECHNIQUES FOR FOURIER TRANSFORM MILLIMETER-WAVE SPECTROSCOPY

摘要

Examples herein include apparatus and techniques that can be used to perform rotational spectroscopy on gas-phase samples. Such techniques can include using a spectrometer providing frequency synthesis and pulse modulation to provide excitation (e.g., pump or probe pulses) of a gas-phase sample at mm-wave frequencies. Synthesis of such mm-wave frequencies can include use of a frequency multiplier, such as an active multiplier chain (AMC). A free induction decay (FID) elicited by the excitation or other time-domain information can be obtained from the sample, such as down-converted and digitized. A frequency domain representation of the digitized information, such as a Fourier transformed representation, can be used to provide a rotational spectrum.

主权项

1. A method, comprising:
exciting a gaseous sample using a first pulsed excitation and a second pulsed excitation each including energy in a mm-wave range of frequencies, the first pulsed excitation and the second pulsed excitation spaced apart in time by a specified duration that is varied between respective measurement cycles, and the first and second pulsed excitations generated at least in part using a frequency multiplier to provide the mm-wave range of frequencies; obtaining respective time-domain representations elicited from the gaseous sample in response to the first and second pulsed excitations corresponding to the respective measurement cycles; determining a collisional relaxation time constant using the respective time-domain representations of the response; and estimating a molecular mass of a species included in the gaseous sample at least in part using the determined collisional relaxation time constant.