Sensitivity and Resolution in Frequency Comb Spectroscopy of Buffer Gas Cooled Polyatomic Molecules

Changala, P. Bryan; Spaun, Ben; Patterson, David; Doyle, John M.; Ye, Jun

doi:10.1007/978-3-319-64346-5_35

Cited by 5 publications

(6 citation statements)

References 34 publications

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“…The method of cryogenic buffer gas cooling is particularly effective for large, heavy molecules (24,25). We have recently demonstrated the integration of a buffer gas cooling source with cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) in the mid-infrared (26,27), which enables sensitive, broadband, high resolution absorption measurements (28,29). We have since extended this apparatus to the longwave infrared (LWIR) region (30) and made significant changes to the buffer gas cooling conditions to permit the preparation and detection of cold, gas-phase samples of even heavier molecules.…”

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Rovibrational quantum state resolution of the C ₆₀ fullerene

Changala

Weichman

Lee³

et al. 2019

Science

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The remarkable physical properties of buckminsterfullerene, C60, have attracted intense research activity since its original discovery. Total quantum state resolved measurements of isolated C60 molecules have been of particularly long-standing interest. However, such observations have to date been unsuccessful due to the difficulty in preparing cold, gas-phase C60 in sufficiently high densities. Here we report high resolution infrared absorption spectroscopy of C60 in the 8.5 µm spectral region. A combination of cryogenic buffer gas cooling and cavityenhanced direct frequency comb spectroscopy has enabled the observation of quantum state resolved rovibrational transitions. Characteristic nuclear spin statistical intensity patterns provide striking confirmation of the indistinguishability of the sixty 12 C atoms, while rovibrational fine structure encodes further details of the molecule's rare icosahedral symmetry. These observations establish new possibilities in the study and control of emergent complexity in finite-sized quantum systems such as fullerenes.One Sentence Summary: High resolution infrared spectroscopy of cold, gas-phase C60 reveals fundamental details of its quantum mechanical structure. Main Text:Understanding molecules as quantum mechanical systems is a central objective of chemical and molecular physics. The complex internal dynamics of these systems evolve over wide energy and time scales as exhibited by the various electronic, vibrational, rotational, and spin degrees of freedom. Polyatomic molecules, in particular, offer the prospect of probing many-body physics in strongly interacting systems. The most comprehensive characterization of a molecular Hamiltonian, which governs intramolecular dynamics, is provided with high resolution spectroscopy. When a polyatomic molecule is sufficiently cold to concentrate the population into and thereby spectrally probe a single rovibrational state, we achieve the unimolecular equivalent of a pure quantum state at absolute zero in the rest frame of the molecule. The precise measurement of transition energies between individual molecular eigenstates yields detailed information about strong, multi-body interactions between atoms in a unimolecular polyatomic lattice, thus providing profound insights into complex molecular structure and ensuing interaction dynamics.Here we report the first rotationally resolved spectrum of buckminsterfullerene, C60. Following the discovery of C60 by Kroto et al. in 1985 (1), infrared and 13 C NMR spectroscopy confirmed its caged, icosahedral structure (2-7). Subsequent spectroscopic and analyticalThe observed fine structure in the infrared spectrum encodes fundamental details of the quantum mechanical structure of C60. To zeroth order, the rotations of C60 can be considered as those of a spherical top with total angular momentum operator J (36). The associated rotational quantum states are ,, J k m , where 0,1, 2, J  is the total angular momentum quantum number, and , , , k m J J    are the projection quantum numbers of the...

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Rovibrational quantum state resolution of the C ₆₀ fullerene

Changala

Weichman

Lee³

et al. 2019

Science

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“…Among others, tunable diode laser absorption spectroscopy, cavity ring-down spectroscopy, cavity-enhanced absorption spectroscopy, and photoacoustic spectroscopy have all successfully been employed in breath analysis but are typically limited in tunability and therefore in the number of detectable analytes [1]. Cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) offers substantially enhanced capabilities for the simultaneous detection of multiple species due to the combination of high spectral resolution, wide spectral coverage, and high sensitivity [13][14][15][16][17][18]. An early study from 2008 demonstrated this by detecting carbon monoxide, carbon dioxide, methane, ammonia, and water in breath samples by CE-DFCS [19].…”

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confidence: 99%

Ultra-sensitive multi-species spectroscopic breath analysis for real-time health monitoring and diagnostics

Liang,

Chan,

Changala

et al. 2021

Preprint

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Breath analysis enables rapid, non-invasive diagnostics, as well as long-term monitoring, of human health through the identification and quantification of exhaled biomarkers. Here, for the first time, we demonstrate the remarkable capabilities of mid-infrared (mid-IR) cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) applied to breath analysis. We simultaneously detect and monitor as a function of time four breath biomarkers -CH3OH, CH4, H2O and HDO -as well as illustrating the feasibility of detecting at least six more (H2CO, C2H6, OCS, C2H4, CS2 and NH3) without modifications to the experimental apparatus. We achieve ultra-high detection sensitivity at the parts-per-trillion level. This is made possible by the combination of the broadband spectral coverage of a frequency comb, the high spectral resolution afforded by the individual comb teeth, and the sensitivity enhancement resulting from a high-finesse cavity. Exploiting recent advances in frequency comb, optical coating, and photodetector technologies, we can access a large variety of biomarkers with strong carbon-hydrogen bond spectral signatures in the mid-IR.

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“…The fast acquisition advantage allows for both real-time remote sensing [1] (seconds) and measurement of fast chemical kinetics [2][3][4][5] (microseconds). These combined advantages have been demonstrated in techniques of cavity-enhanced spectroscopy with a dispersive spectrometer [2][3][4]6]. As alternatives to a dispersive spectrometer, mid-IR DFCS has also been demonstrated with dual-comb spectroscopy [5,[7][8][9][10] and Fourier transform spectroscopy [11][12][13].…”

Section: Introduction a Mid-ir Direct Frequency Comb Spectroscopymentioning

confidence: 99%

“…Relative to shorter mid-IR wavelengths (< 5 m), important molecular targets in atmospheric sciences like the Criegee intermediate [15], NO3 radical [16,17], isoprene [18], and fundamental spectroscopy like buckyball (C60) [19], display significantly larger absorption intensities near 10 m. A comparably important consideration for these larger, complex molecules is that spectroscopic probing at longer infrared wavelengths alleviates spectral congestion due to IVR (intramolecular vibrational redistribution) processes, thus enabling quantum-state resolution [6,20]. These advantages motivate the recent construction of an 8-10 m mid-infrared frequency comb (an optical parametric oscillator (OPO) based on AgGaSe2) for DFCS [21].…”

Section: Introduction a Mid-ir Direct Frequency Comb Spectroscopymentioning

confidence: 99%

Comb-resolved spectroscopy with immersion grating in long-wave infrared

Iwakuni¹,

Bui²,

Niedermeyer³

et al. 2019

Opt. Express

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We have developed a dispersive spectrometer using a compact immersion grating for direct frequency comb spectroscopy in the long-wave infrared region of 8-10 m. A frequency resolution of 463 MHz is achieved, which is the highest reported in this wavelength region with a dispersive direct frequency comb spectrometer. We also demonstrate individual mode-resolved imaging of the frequency comb spectrum by Vernier cavity filtering and apply this to obtain both simple and complex molecular spectra. These results indicate that the immersion grating spectrometer offers the next advancement for sensitive, high-resolution spectroscopy of transient and large/complex molecules when combined with cavity enhancement and cooling techniques.

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Sensitivity and Resolution in Frequency Comb Spectroscopy of Buffer Gas Cooled Polyatomic Molecules

Cited by 5 publications

References 34 publications

Rovibrational quantum state resolution of the C ₆₀ fullerene

Rovibrational quantum state resolution of the C ₆₀ fullerene

Ultra-sensitive multi-species spectroscopic breath analysis for real-time health monitoring and diagnostics

Comb-resolved spectroscopy with immersion grating in long-wave infrared

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Sensitivity and Resolution in Frequency Comb Spectroscopy of Buffer Gas Cooled Polyatomic Molecules

Cited by 5 publications

References 34 publications

Rovibrational quantum state resolution of the C 60 fullerene

Rovibrational quantum state resolution of the C 60 fullerene

Ultra-sensitive multi-species spectroscopic breath analysis for real-time health monitoring and diagnostics

Comb-resolved spectroscopy with immersion grating in long-wave infrared

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Rovibrational quantum state resolution of the C ₆₀ fullerene

Rovibrational quantum state resolution of the C ₆₀ fullerene