Abstract: Apparatus and techniques for broadband Fourier transform spectroscopy can include frequency hopping spread-spectrum spectroscopy approaches. For example, an excitation source power can be spread over a specified frequency bandwidth, such as by applying a sequence of short, transform-limited pulses to a sample. Each pulse can include a specified carrier frequency, and a corresponding bandwidth of the individual pulse can be determined by a frequency domain representation when Fourier transformed. A series of short excitation pulses can be used to create an excitation sequence, such as to deliver a specified or desired amount of power to the sample, such as by having the excitation source enabled for a time comparable to a free induction decay (FID) dephasing time.

Abstract: 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.

Abstract: Apparatus and techniques for broadband Fourier transform spectroscopy can include frequency hopping spread-spectrum spectroscopy approaches. For example, an excitation source power can be spread over a specified frequency bandwidth, such as by applying a sequence of short, transform-limited pulses to a sample. Each pulse can include a specified carrier frequency, and a corresponding bandwidth of the individual pulse can be determined by a frequency domain representation when Fourier transformed. A series of short excitation pulses can be used to create an excitation sequence, such as to deliver a specified or desired amount of power to the sample, such as by having the excitation source enabled for a time comparable to a free induction decay (FID) dephasing time.

Abstract: 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.