Theoretical Investigation of the Reaction of O(D) with Formamide.

Carbamic acid (HNCOOH) is a small organic molecule that is terrestrially unstable in condensed phases under ambient conditions but could survive in the low densities and temperatures of the interstellar medium. In this work, the reaction of formamide (HNCOH) and electronically excited oxygen atoms in the D state, namely, O(D), has been investigated computationally to determine the feasibility of carbamic acid production. Geometries for carbamic acid and other potential reaction products have been calculated, as well as all pertinent transition states.

Millimeter-Wave and High-Resolution Infrared Spectroscopy of the Ground and Seven Lowest Fundamental States of 1-1,2,4-Triazole.

A combined analysis of millimeter-wave (70-700 GHz) and rotationally resolved infrared (400-1200 cm) spectra of the ground state and seven fundamental vibrational modes of 1-1,2,4-triazole is reported. While the lowest-energy vibrationally excited state (ν) is well-treated using a single-state distorted-rotor Hamiltonian, the second (ν) and third (ν) vibrationally excited states are involved in strong -type Coriolis coupling and require an appropriate two-state Hamiltonian. The oblate nature of 1-1,2,4-triazole is sufficiently close to the oblate symmetric-top limit that the analysis requires the use of A-reduced, sextic centrifugally distorted-rotor Hamiltonian models in the I representation in order to achieve low σ values.

Millimeter/Submillimeter-wave Spectroscopy and the Semi-experimental Equilibrium () Structure of 1-1,2,4-Triazole (-CHN).

The millimeter/submillimeter spectrum of 1-1,2,4-triazole is reported from 70 to 700 GHz, providing spectral frequencies directly comparable to radio telescopes and enabling an astronomical search. Using four deuteriated samples of 1,2,4-triazole, we measured, assigned, and least-squares fit transitions for 26 isotopologues to sextic A- and S-reduced Hamiltonians. An accurate and precise semi-experimental () structure from 50 independent moments of inertia has been obtained.

Laser-Induced Chemistry Observed during 248 nm Vacuum Ultraviolet Photolysis of an O and CHNH Mixture.

We present an examination of the 248 nm VUV (vacuum ultraviolet) laser photolysis of an ozone (O) and methylamine (CHNH) mixture as means to produce aminomethanol (NHCHOH). Aminomethanol is predicted to be the direct interstellar precursor to glycine and is therefore an important target for detection in the interstellar medium. However, due to its high reactivity under terrestrial conditions, aminomethanol evades gas-phase spectral detection.

Millimeter/Submillimeter Spectroscopic Detection of Desorbed Ices: A New Technique in Laboratory Astrochemistry.

A new laboratory technique has been developed that utilizes gas-phase, direct-absorption millimeter and submillimeter spectroscopy to detect and identify desorbed species from interstellar and cometary ice analogues. Rotational spectroscopy is a powerful structure-specific technique for detecting isomers and other species possessing the same mass that are indistinguishable with mass spectrometry. Furthermore, the resultant laboratory spectra are directly comparable to observational data from far-infrared and millimeter telescopes.

AC Stark Effect Observed in a Microwave-Millimeter/Submillimeter Wave Double-Resonance Experiment.

Microwave-millimeter/submillimeter wave double-resonance spectroscopy has been developed with the use of technology typically employed in chirped pulse Fourier transform microwave spectroscopy and fast-sweep direct absorption (sub)millimeter-wave spectroscopy. This technique offers the high sensitivity provided by millimeter/submillimeter fast-sweep techniques with the rapid data acquisition offered by chirped pulse Fourier transform microwave spectrometers. Rather than detecting the movement of population as is observed in a traditional double-resonance experiment, instead we detected the splitting of spectral lines arising from the AC Stark effect.

Fast sweep direct absorption (sub)millimeter-wave spectroscopy.

Direct absorption spectroscopy has been the mainstay for spectral acquisition in the millimeter and submillimeter wavelength regimes because of the sensitivity offered by standard hot electron bolometer detectors. However, this approach is limited in its utility because of the slow spectral acquisition speeds. A few rapid acquisition techniques that offer reasonable levels of sensitivity have been developed, but these rely on specialized and costly equipment.

Complex organic molecules along the accretion flow in isolated and externally irradiated protoplanetary disks.

The birth environment of the Sun will have influenced the physical and chemical structure of the pre-solar nebula, including the attainable chemical complexity reached in the disk, important for prebiotic chemistry. The formation and distribution of complex organic molecules (COMs) in a disk around a T Tauri star is investigated for two scenarios: (i) an isolated disk, and (ii) a disk irradiated externally by a nearby massive star. The chemistry is calculated along the accretion flow from the outer disk inwards using a comprehensive network which includes gas-phase reactions, gas-grain interactions, and thermal grain-surface chemistry.

Extending high-finesse cavity techniques to the far-infrared.

Sensitive spectroscopic techniques involving high-finesse Fabry-Perot resonators are widely used in the microwave and near-infrared spectral regimes, but hardware limitations have hindered their extension to far-infrared wavelengths. While there is no theoretical limit to the frequency region where cavity-enhanced techniques are practical, the sensitivity of these methods does depend explicitly on the availability of highly reflective optics and, in the case of cavity ringdown spectroscopy, sufficiently fast detectors. Here, we describe a novel high-finesse cavity that uses wire-grid polarizers as the reflective surfaces.

Multipass millimeter/submillimeter spectrometer to probe dissociative reaction dynamics.

We present here the instrument design and first experimental results from a multipass millimeter/submillimeter spectrometer designed to probe dissociative reaction dynamics. This work focuses on benchmarking the instrument performance through detection of the CH3O and H2CO products from methanol dissociation induced by a high-voltage plasma discharge. Multiple rotational lines from CH3O and H2CO were observed when this plasma discharge was applied to a sample of methanol vapor seeded in an argon supersonic expansion.

Theoretical examination of O((1)D) insertion reactions to form methanediol, methoxymethanol, and aminomethanol.

A computational study of O((1)D) insertion reactions with methanol (CH3OH), dimethyl ether (CH3OCH3), and methyl amine (CH3NH2) was performed to guide laboratory investigations of the insertion product molecules methanediol (HOCH2OH), methoxymethanol (CH3OCH2OH), and aminomethanol (HOCH2NH2), respectively. The minimum energy and higher energy conformer geometries of the products were determined at the MP2/aug-cc-pVTZ level of theory, and CCSD(T)/aug-cc-pVTZ calculations were performed on the reactants, products, and transitions states to examine the insertion reaction energetics. Torsional barriers for internal motion in methanediol, methoxymethanol, and aminomethanol were also determined.

Spatial distributions and interstellar reaction processes.

Methyl formate presents a challenge for the conventional chemical mechanisms assumed to guide interstellar organic chemistry. Previous studies of potential formation pathways for methyl formate in interstellar clouds ruled out gas-phase chemistry as a major production route, and more recent chemical kinetics models indicate that it may form efficiently from radical-radical chemistry on ice surfaces. Yet, recent chemical imaging studies of methyl formate and molecules potentially related to its formation suggest that it may form through previously unexplored gas-phase chemistry.

A quantum cascade laser cw cavity ringdown spectrometer coupled to a supersonic expansion source.

A new instrument has been constructed that couples a supersonic expansion source to a continuous wave cavity ringdown spectrometer using a Fabry-Perot quantum cascade laser (QCL). The purpose of the instrument is to enable the acquisition of a cold, rotationally resolved gas phase spectrum of buckminsterfullerene (C(60)). As a first test of the system, high resolution spectra of the nu(8) vibrational band of CH(2)Br(2) have been acquired at approximately 1197 cm(-1).