39 research outputs found
NEW RESULTS FROM A SPECTRAL-LINE SURVEY OF Sgr B2(N): INSIGHT INTO GAS-PHASE PROCESSES
No full textAuthor Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ 85721A confusion-limited spectral line survey of Sgr B2(N) at 3, 2, and 1 mm (68 - 116, 130 - 172, and 210 - 280 GHz) using the Kitt Peak 12 m and the Submillimeter Telescope (SMT) of the Arizona Radio Observatory has recently been completed. While this data is still being analyzed, interesting new results have already been found. For example, a study of the spectra of CHNH and CHNH has shown that these species, previously thought to be closely-related synthetically, vary greatly in rotational temperature and distribution in Sgr B2(N). Thus the hypothesized grain synthesis of CHNH from CHNH is improbable, and neutral-neutral reactions are the most likely source of these species. These data, as well as other results, also provide insight into the physical structure of the Sgr B2(N) region
THE MILLIMETER/SUBMILLIMETER SPECTRUM OF TiF (X)
No full textAuthor Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ, 85721The pure rotational spectrum of the molecular ion TiF (X) has been measured using a combination of millimeter-wave direct absorption methods and velocity modulation techniques. TiF was created in an AC glow discharge using a mixture of gas-phase TiCl, 10\% F in helium, and argon. In contrast to TiCl, the spectra of TiF were weaker, a probable result of the synthesis method. Ten rotational transitions were measured in the frequency range of 327 to 542 GHz. All three spin-orbit components were observed, which were additionally split into doublets due to fluorine hyperfine interactions. The fine structure exhibited a regular case (a) pattern with minimal second-order spin-orbit effects. These data were fit with a case (a) Hamiltonian and rotational, fine structure, and hyperfine constants were determined. The calculated bond length of TiF was found to be shorter than that of TiF, which is thought to be due to an increase in the effective nuclear charge of titanium
CURRENT RESULTS FROM A SPECTRAL-LINE SURVEY OF SGR B2(N)
No full textAuthor Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ 85721One of the most chemically-rich giant molecular clouds is Sgr B2(N), which is located near the Galactic center. Using the Arizona Radio Observatory (ARO) telescopes, the Kitt Peak 12m and the Submillimeter Telescope (SMT), a spectral-line survey of this object at the confusion limit is being conducted across the entire 1, 2, and 3mm atmospheric windows from 65-280 GHz. The 3 and 1mm data are being collected with ALMA-type sideband separating mixers with unprecedented sensitivity and stability, as well as excellent image rejection. Typical noise levels achieved are 9-15 mK peak-to-peak. This survey is currently 70\% complete. The current data show that several potential prebiotic species, such as acetamide and methyl amine, are present in this source, while others are not. These results indicate that interstellar chemistry follows specific pathways that selectively lead to certain compounds. A preliminary comparison of the currently detected species in Sgr B2(N) to the compounds found in meteorites will also be presented
THE PURE ROTATIONAL SPECTRUM OF TiCl (X) BY VELOCITY MODULATION SPECTROSCOPY
No full textAuthor Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ, 85721The pure rotational spectrum of the molecular ion TiCl (X) has been measured using millimeter-wave direct absorption methods incorporating velocity modulation techniques. This species is the first metal-containing molecular ion observed with millimeter-wave velocity modulation spectroscopy. TiCl was created in an AC glow discharge of gas-phase TiCl and argon. Ten, eleven, and nine rotational transitions of TiCl, TiCl, and TiCl were measured, respectively, in the frequency range of 323 to 424 GHz. All three spin-orbit components were observed. The irregular fine structure splittings indicate that two spin-orbit ladders are perturbed by an excited electronic state. Rotational, spin-orbit, and spin-spin parameters have been determined from the data and agree well with past optical studies. This study illustrates the power of velocity modulation for ion selectivity at millimeter/sub-mm wavelengths
THE SUBMILLIMETER-WAVE SPECTRUM OF THE CrH AND CrD RADICALS
No full textAuthor Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of ArizonaThe transition of CrH and the line of CrD in their ground states have been recorded using submillimeter direct absorption techniques. This study was the first direct measurement of these transitions. These molecules were produced in a discharge plasma of chromium vapor and or gas. Three fine structure components were measured for each radical, and the proton and deuteron hyperfine splittings were also resolved. Spectroscopic constants were obtained by fitting the data with a Hund's case (b) Hamiltonian including rotation, spin-rotation, spin-spin, magnetic hyperfine, and electric quadrupole interactions. These measurements have resulted in improved spectroscopic constants for both isotopomers. The hyperfine parameters suggest that the bonding in CrH has a nonnegligible covalent character. This molecule may be present in the outer envelope of late-type stars and formed by ion-molecule reactions from neutral or ionized Cr and hydrogen gas. Chromium has a cosmic abundance of
A NEW E-BAND (60 - 90 GHz) FOURIER TRANSFORM MILLIMETER-WAVE SPECTROMETER
No full textAuthor Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ 85721An E-band (60 - 90 GHz) cavity Fourier transform millimeter-wave (FTmmW) spectrometer system has been built and used for molecular measurements for the first time. These frequencies are the highest acheived using cavity FTM/mmW techniques. This new system, implemented as a millimeter frequency band on the current FTMW spectrometer of the Ziurys group, utilizes waveguide for radiation propagation and commercial E-band doublers and quadruplers to achieve continuous operation from 60 to 90 GHz. This system also employs an ALMA Band 2 low-noise amplifier (LNA), designed by NRAO. The Fabry-Perot cavity consists of two 170 mm diameter mirrors with a radius of curvature of 840 mm and a separation of 700 mm. The Q factor of the system is around 100,000. Using this system, the N = 4 3 transition of ScC near 62 GHz has been recorded for the first time. These data, as well as other molecular lines, will be presented
THE PURE ROTATIONAL SPECTRUM OF THE MOLECULAR ION FeO (X)
No full textAuthor Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ, 85721The pure rotational spectrum of the FeO (X) molecular ion has been measured using millimeter-wave direct absorption techniques incorporating velocity modulation methods. This work is the first measurement of high-resolution spectra for this ion. This species was created by the reaction of gas-phase Fe(CO) and NO in the presence of argon carrier gas and an AC glow discharge. The strengths of the signals due to FeO were over 50 times less intense than those of FeO. Nine rotational transitions were measured in the frequency range of 300 to 544 GHz. Each transition was found to be split into six fine-structure components, a result of spin-rotation and spin-spin interactions, over a range of 4 GHz. The data have been fit with a case (b) Hamiltonian, and rotational and fine-structure constants were determined. The bond length in FeO appears to be similar to its neutral counterpart (1.641 \AA \ vs. 1.619 \AA), not unexpected given that the two electron configurations differ by a single electron. FeO is a powerful catalytic oxidant in the gas phase, and has been shown to convert methane into methanol
THE SUBMILLIMETER SPECTRUM OF MnH AND MnD (X
No full textAuthor Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ, 85721The N = 0 1 transition of MnH and the N = 2 3 transition of MnD in their ground states have been measured at submillimeter wavelengths from 333 to 517 GHz. The spectra of these molecules were recorded using millimeter-wave direct absorption methods. MnH and MnD were created in the gas phase from manganese vapor, produced with a Broida oven, and H or D in the presence of a DC discharge. Production of these radicals was somewhat problematic, and required extreme heating of the manganese. Fine structure and manganese hyperfine splittings were resolved for both radicals, as well as the hydrogen hyperfine structure for MnH. These spectra are the first pure rotational measurements recorded for these species. The data has been analyzed, and rotation, fine structure, and nuclear hyperfine parameters have been determined. These constants are in reasonable agreement with the past optical and infrared data
THE FOURIER TRANSFORM MICROWAVE/MILLIMETER SPECTRUM OF ScO (X)
No full textAuthor Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ 85721The pure rotational spectra of ScO (X) have been recorded in the 4 - 90 GHz range using Fourier transform microwave/millimeter (FTM/mmW) techniques. This species was created in a supersonic jet expansion of laser-ablated scandium vapor and NO gas, diluted in argon. The N = 1 0 and 2 1 rotational transitions in both v = 0 and 1 have been measured near 30 and 61 GHz, respectively. The data over 60 GHz were obtained using a new E-band (60 - 90 GHz) FTmmW spectrometer system. The data have been analyzed, and rotational, fine, and hyperfine constants have been determined, which are in good agreement with those from past optical studies. ScO is a potential circumstellar molecule in giant/supergiant stars, where it is produced in oxygen-burning nucleosynthesis
FOURIER TRANSFORM MICROWAVE SPECTRUM OF THE YC (XA) RADICAL
No full textAuthor Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ 85721The pure rotational spectrum of YC (XA) in the range 4 - 40 GHz has been measured using Fourier transform microwave (FTMW) techniques. The species was produced using Discharge Assisted Laser Ablation Spectroscopy (DALAS) in a supersonic jet expansion of yttrium vapor and HCCH or CH, diluted in argon carrier gas. Three rotational transitions (N = 1 0, 2 1, and 3 2) have been recorded each exhibiting fine structure and hyperfine splittings due to the yttrium nuclear spin of I(Y) = 1/2. The data have been analyzed wtih a case (b) asymmetric top Hamiltonian, and rotational, fine, and hyperfine constants have been determined. The spectrum of this species was previously measured by PPMODR methods, and our data have refined the spectroscopic constants. Measurements of the C isotopologues are currently underway to establish a precise structure for YC
