Charles R. Markus
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View article: Direct Measurement of the OH + HO<sub>2</sub> Cross Reaction Using Infrared Kinetic Spectroscopy
Direct Measurement of the OH + HO<sub>2</sub> Cross Reaction Using Infrared Kinetic Spectroscopy Open
The cross reaction between the free radicals OH and HO2 plays a critical role in a wide range of environments, including combustion and the atmospheres of Earth and Mars. In the middle atmosphere on Earth, it is the ultimate terminating st…
View article: Direct Frequency Comb Cavity Ring-Down Spectroscopy Using Vernier Filtering
Direct Frequency Comb Cavity Ring-Down Spectroscopy Using Vernier Filtering Open
We present direct frequency comb cavity ring-down spectroscopy with Vernier filtering as a straightforward approach to sensitive and multiplexed trace gas detection. The high finesse cavity acts both to extend the interaction length with t…
View article: Cavity-enhanced dual-comb spectroscopy in the molecular fingerprint region using free-running quantum cascade lasers
Cavity-enhanced dual-comb spectroscopy in the molecular fingerprint region using free-running quantum cascade lasers Open
Cavity-enhanced dual-comb spectroscopy promises broadband, high-resolution, and highly sensitive spectroscopic measurements on sub-millisecond timescales, making it highly attractive for trace gas monitoring. In this work, we demonstrate c…
View article: Correction to “OH Roaming and Beyond in the Unimolecular Decay of the Methyl-Ethyl-Substituted Criegee Intermediate: Observations and Predictions”
Correction to “OH Roaming and Beyond in the Unimolecular Decay of the Methyl-Ethyl-Substituted Criegee Intermediate: Observations and Predictions” Open
ADVERTISEMENT RETURN TO ARTICLES ASAPPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to "OH Roaming and Beyond in the Unimolecular Decay of the Methyl-Ethyl-Substituted Criegee Intermediate: Observations an…
View article: Bimolecular Reaction of Methyl-Ethyl-Substituted Criegee Intermediate with SO<sub>2</sub>
Bimolecular Reaction of Methyl-Ethyl-Substituted Criegee Intermediate with SO<sub>2</sub> Open
Methyl-ethyl-substituted Criegee intermediate (MECI) is a four-carbon carbonyl oxide that is formed in the ozonolysis of some asymmetric alkenes. MECI is structurally similar to the isoprene-derived methyl vinyl ketone oxide (MVK-oxide) bu…
View article: OH Roaming and Beyond in the Unimolecular Decay of the Methyl-Ethyl-Substituted Criegee Intermediate: Observations and Predictions
OH Roaming and Beyond in the Unimolecular Decay of the Methyl-Ethyl-Substituted Criegee Intermediate: Observations and Predictions Open
Alkene ozonolysis generates short-lived Criegee intermediates that are a significant source of hydroxyl (OH) radicals. This study demonstrates that roaming of the separating OH radicals can yield alternate hydroxycarbonyl products, thereby…
View article: Cavity-Enhanced Vernier Spectroscopy with a Chip-Scale Mid-Infrared Frequency Comb
Cavity-Enhanced Vernier Spectroscopy with a Chip-Scale Mid-Infrared Frequency Comb Open
Chip-scale optical frequency combs can provide broadband spectroscopy for diagnosing complex organic molecules. They are also promising as miniaturized laser spectrometers in applications ranging from atmospheric chemistry to geological sc…
View article: Cavity-Enhanced Vernier Spectroscopy with a Chip-Scale Mid-Infrared Frequency Comb
Cavity-Enhanced Vernier Spectroscopy with a Chip-Scale Mid-Infrared Frequency Comb Open
Chip-scale optical frequency combs can provide broadband spectroscopy for diagnosing complex organic molecules. They are also promising as miniaturized laser spectrometers in applications ranging from atmospheric chemistry to geological sc…
View article: Cavity-Enhanced Vernier Spectroscopy with a Chip-Scale Mid-Infrared\n Frequency Comb
Cavity-Enhanced Vernier Spectroscopy with a Chip-Scale Mid-Infrared\n Frequency Comb Open
Chip-scale optical frequency combs can provide broadband spectroscopy for diagnosing complex organic molecules. They are also promising as miniaturized laser spectrometers in applications ranging from atmospheric chemistry to geological sc…
View article: Mid-Infrared Cross-Comb Spectroscopy
Mid-Infrared Cross-Comb Spectroscopy Open
Dual-comb spectroscopy has been proven a powerful tool in molecular characterization, which remains challenging to implement in the mid-infrared region due to difficulties in the realization of two mutually locked comb sources and efficien…
View article: MEASUREMENT OF THE <i>&#195;</i>&#8592;<i>&#126;X</i> BAND OF 1- AND 2-METHYLALLYL RADICALS USING CAVITY RINGDOWN SPECTROSCOPY
MEASUREMENT OF THE <i>Ã</i>←<i>~X</i> BAND OF 1- AND 2-METHYLALLYL RADICALS USING CAVITY RINGDOWN SPECTROSCOPY Open
The reduced reactivity of resonance-stabilized hydrocarbon radicals allows for them to reach higher concentrations in harsh environments such as flames or planetary atmospheres. Reactions between them remain rapid and could explain the for…
View article: NOISE IMMUNE CAVITY ENHANCED OPTICAL HETERODYNE ZEEMAN MODULATION SPECTROSCOPY
NOISE IMMUNE CAVITY ENHANCED OPTICAL HETERODYNE ZEEMAN MODULATION SPECTROSCOPY Open
Of the roughly 210 species detected outside our Solar System, about a quarter of them are radicals. Radicals are sensitive probes of their chemical and physical environments and have been implicated in the formation of complex organic mole…
View article: DIRECT FREQUENCY COMB CAVITY ENHANCED SPECTROSCOPY FOR TRACE GAS DETECTION USING MID-INFRARED INTERBAND CASCADE LASERS
DIRECT FREQUENCY COMB CAVITY ENHANCED SPECTROSCOPY FOR TRACE GAS DETECTION USING MID-INFRARED INTERBAND CASCADE LASERS Open
Optical frequency combs provide broadband coverage while still being able to take full advantage of cavity-enhanced methods. The mid-infrared is highly desirable for molecular spectroscopy, where many strong fundamental vibrational bands e…
View article: Pure Rotational Spectrum of CCl<sup>+</sup>
Pure Rotational Spectrum of CCl<sup>+</sup> Open
The pure rotational spectrum of the CCl + ( X 1 Σ + ) cation has been observed for the first time using a cryogenic ion trap apparatus and applying an action spectroscopy scheme. The major isotopic species 12 C 35 Cl + was observed up to t…
View article: Mode-resolved Cavity-enhanced Vernier Spectroscopy Using an Interband Cascade Laser Frequency Comb
Mode-resolved Cavity-enhanced Vernier Spectroscopy Using an Interband Cascade Laser Frequency Comb Open
We demonstrate a mid-IR mode-resolved Vernier optical frequency comb spectrometer with an interband cascade laser source. The free-running system provides 35 meters of effective path length for monitoring 1-THz-broad spectra at 3.63 µm.
View article: INDIRECT ROTATIONAL SPECTROSCOPY OF THE D2H+ MOLECULAR ION
INDIRECT ROTATIONAL SPECTROSCOPY OF THE D2H+ MOLECULAR ION Open
The partially deuterated isotopologues of H$_3^+$ have proven to be valuable probes of interstellar environments. In low temperature regions ($< 20$ K) such as dark molecular clouds, deuterium fractionation leads the ratios of \\chem{D_2H^…
View article: SUB-DOPPLER SPECTROSCOPY OF THE ν2 FUNDAMENTAL BAND AND FIRST HOT BAND OF THE H3+ CATION
SUB-DOPPLER SPECTROSCOPY OF THE ν2 FUNDAMENTAL BAND AND FIRST HOT BAND OF THE H3+ CATION Open
The simplest polyatomic molecule, \\chem{H_3^+}, serves as an important benchmark for \\textit{ab initio} theory and is an important constituent of the interstellar medium (ISM). In the ISM, \\chem{H_3^+} initiates a chain of ion-neutral r…
View article: SUB-DOPPLER SPECTROSCOPY OF THE ν3 BAND OF METHANE
SUB-DOPPLER SPECTROSCOPY OF THE ν3 BAND OF METHANE Open
Methane has been observed in brown dwarfs\\footnote{B. Oppenheimer, S. Kulkarni, K. Matthews \\textit{et al.}, \\textit{Astrophys. J.} (1998), \\textbf{502(2)}, 932-943.} and planetary atmospheres, including planets in our solar system\\fo…
View article: SUB-DOPPLER ROVIBRATIONAL SPECTROSCOPY OF THE H3+ CATION AND ISOTOPOLOGUES
SUB-DOPPLER ROVIBRATIONAL SPECTROSCOPY OF THE H3+ CATION AND ISOTOPOLOGUES Open
Molecular ions play a central role in the chemistry of the interstellar medium (ISM) and act as benchmarks for state of the art textit{ab initio} theory. The molecular ion H$_3^+$ initiates a chain of ion-neutral reactions which drives che…
View article: CAVITY-ENHANCED SPECTROSCOPY OF MOLECULAR IONS IN THE MID-INFRARED WITH UP-CONVERSION DETECTION AND BREWSTER-PLATE SPOILERS
CAVITY-ENHANCED SPECTROSCOPY OF MOLECULAR IONS IN THE MID-INFRARED WITH UP-CONVERSION DETECTION AND BREWSTER-PLATE SPOILERS Open
Molecular ions are challenging to study with conventional spectroscopic methods. Laboratory discharges produce ions in trace quantities which can be obscured by the abundant neutral molecules present. The technique Noise Immune Cavity Enha…
View article: Improving cavity-enhanced spectroscopy of molecular ions in the mid-infrared with up-conversion detection and Brewster-plate spoilers
Improving cavity-enhanced spectroscopy of molecular ions in the mid-infrared with up-conversion detection and Brewster-plate spoilers Open
The performance of sensitive spectroscopic methods in the mid-IR is often limited by fringing due to parasitic etalons and the background noise in mid-infrared detectors. In particular, the technique Noise Immune Cavity Enhanced Optical He…
View article: HIGH PRECISION ROVIBRATIONAL SPECTROSCOPY OF OH<sup>+</sup>
HIGH PRECISION ROVIBRATIONAL SPECTROSCOPY OF OH<sup>+</sup> Open
The molecular ion OH + has long been known to be an important component of the interstellar medium. Its relative abundance can be used to indirectly measure cosmic ray ionization rates of hydrogen, and it is the first intermediate in the i…