Design and evaluation of a pulsed-jet chirped-pulse millimeter-wave spectrometer for the 70–102 GHz region

Park, G. Barratt; Steeves, Adam H.; Prozument, Kirill; Neill, Justin L.; Field, Robert W.

doi:10.1063/1.3597774

Cited by 73 publications

(91 citation statements)

References 41 publications

(47 reference statements)

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“…A single chirp can contain ~10 5 15 resolution elements. [1][2][3] Since all two-level systems within the chirp frequency region are sampled in each chirp, relative transition intensities may be measured with accuracies approaching the 1% level, even for transition frequencies separated by 10 GHz. 20 The microwave electric field,  0 , scales as I 1/2 , where I is the intensity in units of power/area.…”

Section: B Chirped Pulse Spectroscopymentioning

confidence: 99%

“…Chirped-Pulse millimetre-Wave (CPmmW) spectroscopy [1][2][3] is capable of determining the relative species-conformervibrational level populations of all polar products of a photolysis reaction. These experimentally determined populations encode the structures of the transition states 25 that are most important at each photolysis wavelength or combination of wavelengths.…”

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A new approach toward transition state spectroscopy

et al. 2013

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10Chirped-Pulse millimetre-Wave (CPmmW) rotational spectroscopy provides a new class of information about photolysis transition state(s). Measured intensities in rotational spectra determine species-isomervibrational populations, provided that rotational populations can be thermalized. The formation and detection of S 0 vinylidene is discussed in the limits of low and high initial rotational excitation. CPmmW 15 spectra of 193 nm photolysis of Vinyl Cyanide (Acrylonitrile) contain J=0-1 transitions in more than 20 vibrational levels of HCN, HNC, but no transitions in vinylidene or highly excited local-bender vibrational levels of acetylene. Reasons for the non-observation of the vinylidene co-product of HCN are discussed. A. Introduction 20Chirped-Pulse millimetre-Wave (CPmmW) spectroscopy 1-3 is capable of determining the relative species-conformervibrational level populations of all polar products of a photolysis reaction. These experimentally determined populations encode the structures of the transition states 25 that are most important at each photolysis wavelength or combination of wavelengths. 4 The isomer-conformervibrational level population information obtained from a CPmmW spectrum is more complete than what is obtainable by mass spectrometry 5 and free of the need for 30 the transition strength and quantum yield determinations that are required for most laser-based population measurements. However, difficulties exist in the use of populations determined by CPmmW spectroscopy to characterize transition states. B. Chirped Pulse SpectroscopyChirped Pulse Fourier Transform Microwave Spectroscopy 55 is a revolutionary technique developed in the research group of Brooks Pate at the University of Virginia. 2,3 In its initial implementation, the frequency of a microwave pulse is chirped linearly in time over several GHz. This microwave pulse is broadcast into a gas phase molecular 60 sample, polarizing all two-level systems with frequencies within the spectral interval of the chirped pulse. These polarizations relax by Free Induction Decay (FID), which is a voltage vs. time signal that is collected, downconverted by mixing with a local oscillator (heterodyne where  is the electric dipole moment,  0 is the peak microwave electric field, N 1,2 is the population density 75 difference between levels 1 and 2,  is the chirp rate, A is

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Section: B Chirped Pulse Spectroscopymentioning

confidence: 99%

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A new approach toward transition state spectroscopy

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“…The CPmmW spectrometer is described in Ref. 17, so we will omit the details here. The UV radiation was generated by a pulsed dye laser (Lambda Physik FL3002E), operating with Coumarin 440 dye, pumped by the 355 nm third harmonic of an Nd:YAG laser (Spectra-Physics DCR-3).…”

Section: A Millimeter-wave Optical Double Resonance Configurationmentioning

confidence: 99%

“…When monitoring millimeter-wave transitions of the ground state, mmODR information can be used for unambiguous identification of the lower level involved in the optical transition, because a double resonance signal indicates that the millimeter-wave transition and the optical transition share a common level. The frequency-agility of our chirpedpulse millimeter wave (CPmmW) spectrometer, 17 based on the Pate design, 18,19 allows us to perform multiplexed mmODR, where more than one millimeter-wave transition is monitored simultaneously, and we demonstrate the effectiveness of multiplexed mmODR schemes for rapid acquisition and rotational assignment of three predissociated levels of theC state of SO 2 between 46 800 and 47 650 cm −1 . We have also made a millimeter-wave implementation of the background free coherence-converted population transfer (CCPT) technique.…”

Section: Introductionmentioning

confidence: 99%

Millimeter-wave optical double resonance schemes for rapid assignment of perturbed spectra, with applications to the C̃1B2 state of SO2

Park

Womack

Whitehill

et al. 2015

The Journal of Chemical Physics

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Millimeter-wave detected, millimeter-wave optical double resonance (mmODR) spectroscopy is a powerful tool for the analysis of dense, complicated regions in the optical spectra of small molecules. The availability of cavity-free microwave and millimeter wave spectrometers with frequency-agile generation and detection of radiation (required for chirped-pulse Fourier-transform spectroscopy) opens up new schemes for double resonance experiments. We demonstrate a multiplexed population labeling scheme for rapid acquisition of double resonance spectra, probing multiple rotational transitions simultaneously. We also demonstrate a millimeter-wave implementation of the coherenceconverted population transfer scheme for background-free mmODR, which provides a ∼10-fold sensitivity improvement over the population labeling scheme. We analyze perturbations in theC state of SO 2 , and we rotationally assign a b 2 vibrational level at 45 328 cm −1 that borrows intensity via a c-axis Coriolis interaction. We also demonstrate the effectiveness of our multiplexed mmODR scheme for rapid acquisition and assignment of three predissociated vibrational levels of theC state of SO 2 between 46 800 and 47 650 cm −1 . C 2015 AIP Publishing LLC. [http://dx

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“…To this end, we have developed a new instrument based on a uniform supersonic flow system 7 combined with a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer. [8][9][10][11][12][13] This chirped-pulse, uniform flow (CPUF) instrument can record ultra-broadband rotational spectra at MHz resolution for transient and rotationally thermalized reaction products. CP-FTMW is a very general spectroscopic method suitable for essentially any species that possesses at least a modest electric dipole moment.…”

Section: Introductionmentioning

confidence: 99%

A chirped-pulse Fourier-transform microwave/pulsed uniform flow spectrometer. I. The low-temperature flow system

Oldham

Abeysekera

Joalland

et al. 2014

The Journal of Chemical Physics

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We report the development of a new instrument that combines chirped-pulse microwave spectroscopy with a pulsed uniform supersonic flow. This combination promises a nearly universal detection method that can deliver isomer and conformer specific, quantitative detection and spectroscopic characterization of unstable reaction products and intermediates, product vibrational distributions, and molecular excited states. This first paper in a series of two presents a new pulsed-flow design, at the heart of which is a fast, high-throughput pulsed valve driven by a piezoelectric stack actuator. Uniform flows at temperatures as low as 20 K were readily achieved with only modest pumping requirements, as demonstrated by impact pressure measurements and pure rotational spectroscopy. The proposed technique will be suitable for application in diverse fields including fundamental studies in spectroscopy, kinetics, and reaction dynamics. © 2014 AIP Publishing LLC.

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Design and evaluation of a pulsed-jet chirped-pulse millimeter-wave spectrometer for the 70–102 GHz region

Cited by 73 publications

References 41 publications

A new approach toward transition state spectroscopy

A new approach toward transition state spectroscopy

Millimeter-wave optical double resonance schemes for rapid assignment of perturbed spectra, with applications to the C̃1B2 state of SO2

A chirped-pulse Fourier-transform microwave/pulsed uniform flow spectrometer. I. The low-temperature flow system

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