A5018038616- Molecular Spectroscopy and Structure
- Atmospheric Ozone and Climate
- Advanced Chemical Physics Studies
- Spectroscopy and Laser Applications
- Astrophysics and Star Formation Studies
- Quantum, superfluid, helium dynamics
- Atomic and Molecular Physics
- Atomic and Subatomic Physics Research
- Various Chemistry Research Topics
- Molecular spectroscopy and chirality
- Chemical Reactions and Mechanisms
- Mass Spectrometry Techniques and Applications
- Nuclear Physics and Applications
- Gamma-ray bursts and supernovae
- Field-Flow Fractionation Techniques
- Advanced Chemical Sensor Technologies
- Astro and Planetary Science
- Analytical Chemistry and Chromatography
- Acoustic Wave Resonator Technologies
- Laser Design and Applications
- Engineering Education and Curriculum Development
- Computational Physics and Python Applications
- Analytical Chemistry and Sensors
- Innovative Educational Techniques
- Online and Blended Learning
University of California, Davis
2014-2025
Natera (United States)
2024
Center for Astrophysics Harvard & Smithsonian
2013-2016
Harvard University
2013-2016
NOAA Chemical Sciences Laboratory
2016
University of Illinois Urbana-Champaign
2009-2015
University of Arizona
2014
Radboud University Nijmegen
2009
Stockholm University
2009
AlbaNova
2009
The detection of E-cyanomethanimine (E-HNCHCN) toward Sagittarius B2(N) is made by comparing the publicly available Green Bank Telescope (GBT) PRIMOS survey spectra to laboratory rotational from a reaction product screening experiment. experiment uses broadband molecular spectroscopy monitor products produced in an electric discharge source using gas mixture NH3 and CH3CN. Several transition frequency coincidences between previously unassigned interstellar transitions have been assigned...
A number of research groups have recently succeeded in producing the simple carbonyl oxides H2COO and CH3CHOO sufficient quantity to observe them spectroscopically probe kinetics their reactions with NO2 SO2. These latter studies provide evidence that play an important role atmosphere, likely contributing pollutant removal, aerosol formation, planetary cooling. In this work, Fourier transform microwave double-resonance spectroscopy are combined theory study five isotopic species H2C═O–O, a...
Because of its structural specificity, rotational spectroscopy has great potential as an analytical tool for characterizing the chemical composition complex gas mixtures. However, disentangling individual molecular constituents a spectrum, especially if many lines are entirely new or unknown, remains challenging. In this paper, we describe empirical approach that combines complementary strengths two techniques, broadband chirped-pulse Fourier transform microwave and narrowband cavity...
Thionitrous acid (HSNO), a potential key intermediate in biological signaling pathways, has been proposed to link NO and H2S biochemistries, but its existence stability vivo remain controversial. We establish that HSNO is spontaneously formed high concentration when gases are mixed at room temperature the presence of metallic surfaces. Our measurements reveal by reaction + N2O3 → HNO2, where product disproportionation. These studies also suggest further with may form HNO HSSH. The length S-N...
The excitation temperature T01 derived from the relative intensities of J = 0 (para) and 1 (ortho) rotational levels H2 has been assumed to be an accurate measure kinetic in interstellar environments. In diffuse molecular clouds, average value is ∼70 K. However, T(H+3) (J, K) (1, 1) 0) H+3 observed ∼30 K same types this work, we present observations three additional cloud sight lines for which measurements are available, showing that four five cases discrepant. We then examine thermalization...
Combustion and pyrolysis processes of allene propyne are known to involve radicals with the structural formula C3H5, most stable which is classic resonance-stabilized allyl radical. In addition allyl, four other isomers C3H5 possible: propene derivatives Z-1-propenyl, E-1-propenyl, 2-propenyl, as well cyclopropane derivative cyclopropyl. Among these 5 species, radical has been extensively studied both theoretically spectroscopically; however, little about spectroscopy cyclopropyl radical,...
Owing to its unparalleled structural specificity, rotational spectroscopy is a powerful technique unambiguously identify and characterize volatile, polar molecules. We present here new experimental approach, automated microwave double resonance (AMDOR) spectroscopy, rapidly determine the constants of these compounds without priori knowledge elemental composition or molecular structure. This task achieved by acquiring classical (frequency vs. intensity) broadband spectrum molecule using...
We have performed measurements of the dissociative electron recombination (DR) ${\mathrm{H}}_{3}^{+}$ at ion storage ring TSR utilizing a supersonic expansion source. The source has been characterized by continuous wave cavity ring-down spectroscopy. present high-resolution DR rate coefficients for different nuclear spin modifications combined with precise fragment imaging studies internal excitation ions inside ring. resolve changes in energy dependence between ortho-${\mathrm{H}}_{3}^{+}$...
The performance of a new K band microwave spectrometer is demonstrated by investigating the rotational spectrum methyl tert -butyl ether, including isotopologues and torsionally excited state.
The nuclear spin dependence of the chemical reaction H(3)(+)+ H(2) → + H(3)(+) has been studied in a hollow cathode plasma cell. Multipass infrared direct absorption spectroscopy employed to monitor populations several low-energy rotational levels ortho- and para-H(3)(+) (o-H(3)(+) p-H(3)(+)) hydrogenic plasmas varying para-H(2) (p-H(2)) enrichment. ratio rates proton hop (k(H)) hydrogen exchange (k(E)) reactions α ≡ k(H)/k(E) is inferred from observed p-H(3)(+) fraction as function p-H(2)...
A Glimpse of HOON Bonds between two oxygen atoms are relatively weak, as manifested in the sometimes explosive reactivity O 2 and various peroxides. Thus, although nitrous acid (HONO) can be rearranged on paper to an isomer with O-O rather than N-O bond, nitrosyl-O-hydroxide (HOON) has been considered too unstable observed. Crabtree et al. (p. 1354 ) used microwave spectroscopy detect formation a dilute gaseous mixture NO OH neon. Isotopic substitutions enabled determination its structure,...
The determination of the dissociative recombination rate coefficient H(3) (+) has had a turbulent history, but both experiment and theory have recently converged to common value. Despite this convergence, it not been clear if there should be difference between coefficients for ortho-H(3) para-H(3) (+). A predicted theoretically could conceivably impact ortho:para ratio in diffuse interstellar medium, where widely observed. We present results an at CRYRING ion storage ring which we...
The chemistry in the diffuse interstellar medium (ISM) initiates gradual increase of molecular complexity during life cycle matter. A key molecule that enables build-up new bonds and molecules via proton donation is H. Its evolution tightly related to hydrogen thought be well understood. However, recent observations ortho para lines H2 H ISM showed a puzzling discrepancy nuclear spin excitation temperatures populations between these two species. H, unlike H2, seems out thermal equilibrium,...
An imaging system with a wide-angle tangential view of the full poloidal cross-section tokamak in simultaneous infrared and visible light has been installed on DIII-D. The optical train includes three polished stainless steel mirrors vacuum, which through an aperture first mirror, similar to design concept proposed for ITER. A dichroic beam splitter outside vacuum separates (IR) light. Spatial calibration is accomplished by warping CAD-rendered image align landmarks data image. IR camera...
HOCO is an important intermediate in combustion and atmospheric processes because the OH + CO → H CO2 reaction represents final step for production of hydrocarbon oxidation, theoretical studies predict that this proceeds via various intermediates, most being radical. Isotopic investigations trans- cis-HOCO have been undertaken using Fourier transform microwave spectroscopy millimeter-wave double resonance techniques combination with a supersonic molecular beam discharge source to better...
Broadband microwave spectra of N-ethyl maleimide (NEM) and succinimide (NES) have been recorded using chirped pulse Fourier transform spectroscopy in the Ka-band (26.5–40 GHz). The for both molecules were fit to a Watson A-reduced Hamiltonian Ir representation obtain best experimental rotational constants (NEM: A0 = 2143.1988(29), B0 1868.7333(22), C0 1082.98458(36); NES: 2061.47756(14), 1791.73517(12), 1050.31263(11)), centrifugal distortion constants, nuclear quadrupole coupling constants....
The chemical reaction H(3)(+) + H(2) → is the simplest bimolecular involving a polyatomic, yet complex enough that exact quantum mechanical calculations to adequately model its dynamics are still unfeasible. In particular, branching fractions for "identity," "proton hop," and "hydrogen exchange" pathways unknown, date, experimental measurements of this process have been limited. work, nuclear-spin-dependent steady-state kinetics examined in detail, employed generate models ortho:para ratio...
Diffuse interstellar bands (DIBs) are absorption features observed in optical and near-infrared spectra that thought to be associated with carbon-rich polyatomic molecules gas. However, because the central wavelengths of these do not correspond electronic transitions any known atomic or molecular species, their nature has remained uncertain since discovery almost a century ago. Here we report on unusually strong DIBs broad-lined Type Ic supernova SN 2012ap exhibit changes equivalent width...
Sulfoxylic acid (HOSOH), a chemical intermediate roughly midway along the path between highly reduced (H2S) and oxidized sulfur (H2SO4), has been detected using Fourier transform microwave spectroscopy double resonance techniques, guided by new high-level CCSD(T) quantum-chemical calculations of its molecular structure. Rotational spectra two most stable isomers HOSOH, putative ground state with C2 symmetry low-lying C(s) rotamer, have measured to high precision up 71 GHz, allowing accurate...
Recent observations of H2 and H3+ in diffuse interstellar sightlines revealed a difference the nuclear spin excitation temperatures two species. This discrepancy comes as surprise, should undergo frequent thermalizing collisions molecular clouds. Non-thermal behavior fundamental / collision system at low was considered possible cause for observed irregular populations. Here, we present measurements steady-state ortho/para ratio with molecules temperature-variable radiofrequency ion trap...
Abstract The phenyl radical (C 6 H 5 . ) is the prototypical σ‐type aryl and one of most common aromatic building blocks for larger ring molecules. Using a combination rotational spectroscopy singly substituted isotopic species vibrational corrections calculated theoretically, an extremely accurate molecular structure has been determined. Relative to benzene, substantially C‐C ipso ‐C bond angle [125.8(3)° vs. 120°], shorter distance [2.713(3) Å 2.783(2) Å] between para carbon atoms.
Carbenes are reactive molecules of the form R(1)-:C-R(2) that play a role in topics ranging from organic synthesis to gas-phase oxidation chemistry. We report first experimental structure determination dihydroxycarbene (HO-:C-OH), one smallest stable singlet carbenes, using combination microwave rotational spectroscopy and high-level coupled-cluster calculations. The semi-experimental equilibrium derived five isotopic variants HO-:C-OH contains two very short CO single bonds (ca. 1.32 Å)....
Succinimide and its derivatives are cyclic five-membered rings that appear in a variety of natural products widely used organic synthesis. From structural standpoint, succinimide contains an NH group the ring which interacts with two adjacent carbonyl groups, pushing structure toward planarity at expense increasing strain eclipsing interactions among out-of-plane hydrogen atoms CH2 groups. Previous quantum chemical calculations different levels theory have predicted both nonplanar C2 planar...
The formation mechanisms of silicon nitride and nitrogen hydrogen films, both produced by chemical vapor deposition (CVD) techniques widely used in electronic device fabrication, are poorly understood. Identification gas-phase intermediates formed from starting materials, typically silane, ammonia, and/or nitrogen, is a critical step assessing the interplay between gas surface processes film formation. Two potential this process, HSiNSi H3SiNSi, have now been detected molecular beam means...