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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Rotational spectra of the X 2Sigma(+) states of CaH and CaD

The rotational spectra of the 2Sigma(2+) ground states of calcium monohydride and monodeuteride have been recorded in absorption between 250 and 700 GHz. The gas phase free radicals have been produced in a ceramic furnace by the reaction of elemental calcium with molecular hydrogen or deuterium in the presence of an electrical discharge. The molecular constants including the rotational constant, centrifugal distortion constants, spin-rotation constants, and magnetic hyperfine interaction constants have been extracted from the spectra.

Frum, C. I.↗
NASA NTRS1982

The rotational spectra of HOCO/plus/, HOCN, HN3, and HNCO from quantum mechanical calculations

Ab initio molecular orbital theory has been used to determine the equilibrium geometries, rotational constants, and rotational spectra of four isoelectronic molecules. Two of these, HOCO(plus) and HOCN, are candidate interstellar molecules. The other two, HNCO and HN3, have known rotational constants. Theoretical rotational constants and spectra for the two unknown species were corrected with the mean experimental to theoretical ratios from the two known species. This procedure resulted in predicted frequencies of 83.75 plus or minus 0.2 GHz for the 4(04) to 3(03) transition in HOCN and 85.08 plus or minus 0.2 GHz for the same transition in HOCO(plus). These are the central lines of triplets whose other members are the 4(14) to 3(13) and 4(13) to 3(12) transitions. The triplet splittings were predicted to be 0.36 plus or minus 0.01 GHz for HOCN and 0.33 plus or minus 0.01 GHz for HOCO(plus). These results indicate that HOCO(plus) is a better candidate for the source of a series of lines reported by Thaddeus, Guelin, and Linke than is HOCN.

Defrees, D. J.↗
NASA NTRS1978

Infrared vibration-rotation spectra of the ClO radical using tunable diode laser spectroscopy

Tunable diode laser spectroscopy is used to measure the infrared vibration-rotation spectra of the ClO radical. The radical is generated in a flow system where a Cl2-He mixture passes through a microwave discharge to dissociate the Cl2. An O3-O2 mixture from an ozone generator is injected into the system downstream of the microwave discharge where O3 combines with Cl to form ClO. By adjusting the gas flow rates to yield an excess of Cl atoms, all the ozone is combined. ClO concentration is measured with UV absorption at 2577 and 2772 A and a deuterium lamp as a continuous source. Total cell pressure is 5.5 torr. The diode laser spectrometer is calibrated with ammonia lines as a reference where possible. The frequency of vibration-rotation lines is expressed as a function of rotational quantum number, fundamental vibrational frequency, and the rotational constants of the upper and lower vibrational states.

Rogowski, R. S.↗
NASA NTRS2000

The Rotational Spectra of IO X(sub 1) (sup 2)pi(sub 3/2), v <= 13 and X(sub 2) (sup 2)pi(sub 1/2), v <= 9

The rotational spectra of IO in vibrational states up to v = 13 in the X(sub 1) (sup 2)pi(sub 3/2) state and up to v = 9 in the X2 (sup 2)pi(sub 1/2) state have been observed in an O2 discharge over molecular I2. In addition, I(18)O has been observed for both the X(sub 1) and X(sub 2) states up to v = 5. All data have been analyzed simultaneously with fixed isotopic ratios among the constants. This extends the data set for the X(sub 1) state described last year at this meeting and provides the first high resolution data for the X(sub 2) state and for I(18)O. An extensive set of parameters has been derived. These will be interpreted in terms of the electronic structure and the interatomic potential.

Miller, Charles E.↗
NASA NTRS1993

Rotational Spectra of the X states of CaH and CaD

The molecular constants including the rotaional constant, centrifugal distortion constants, spin-rotation constants, and magnetic hyperfine interaction constants have been extrcted from the spectra.

Rotation↗
NASA NTRS1992

Ab initio predictions on the rotational spectra of carbon-chain carbene molecules

We predict rotational constants for the carbon-chain molecules H2C=(C=)nC, n=3-8, using ab initio computations, observed values for the earlier members in the series, H2CCC and H2CCCC with n=1 and 2, and empirical geometry corrections derived from comparison of computation and experiment on related molecules. H2CCC and H2CCCC have already been observed by radioastronomy; higher members in the series, because of their large dipole moments, which we have calculated, are candidates for astronomical searches. Our predictions can guide searches and assist in both astronomical and laboratory detection.

NASA Discipline Number 52-10↗
NASA NTRS1984

Theory of collision-induced translation-rotation spectra: H2-He

An adiabatic quantal theory of spectral line shapes in collision-induced absorption and emission is presented which incorporates the induced translation-rotation and translation-vibration spectra. The generalization to account for the anisotropy of the scattering potential is given. Calculations are carried out of the collision-induced absorption spectra of He in collisions with H2 with ab initio electric dipole functions and realistic potentials. The anisotropy of the interaction potential is small and is not included in the calculations. The predicted spectra are in satisfactory agreement with experimental data though some deviations occur which may be significant. The rotational line shapes have exponential wings and are not Lorentzian. The connection between the quantal and classical theories is written out explicitly for the isotropic overlap induction.

Birnbaum, G.↗
NASA NTRS2002

The Submillimeter-wave Rotational Spectra of Interstellar Molecules

We discuss past and recent progress in our long-term laboratory program concerning the submillimeter-wave rotational spectroscopy of known and likely interstellar molecules, especially those associated with regions of high-mass star formation. Our program on the use of spectroscopy to study rotationally inelastic collisions of interstellar interest is also briefly mentioned.

Herbst, Eric↗
NASA NTRS1982

The rotational spectra of HCNH/+/ and COH/+/ from quantum mechanical calculations

A description is provided of ab initio molecular orbital calculations designed to provide accurate predictions for the J = 1 to 0 rotational line of the candidate interstellar molecules HCNH(+) and COH(+). The former is believed to be important in the formation of both HCN and HNC in the interstellar medium. The latter, a metastable isomer of HCO(+), was first proposed as an interstellar molecule by Herbst et al. (1976). Attention is given to thermochemical arguments that this molecule can be formed in the same reactions which are proposed to form HCO(+), taking into account theoretical data which establish its stability to intramolecular rearrangement. Rotational constants are derived by applying an empirical correction to the ab initio rotational constants.

Defrees, D. J.↗
NASA NTRS1994

Hubble Space Telescope Goddard high-resolution spectrograph H2 rotational spectra of Jupiter's aurora

We have observed the emission spectrum from Jupiter's north auroral atmosphere with 0.57 A spectral resolution over 1204-1241 A. Bright emissions have been detected from 50 deg to 60 deg latitude at locations consistent with 6 to 30 R (sub J) auroral ovals, with much fainter emissions away form the auroral ovals. The emission spectrum is well fitted by both laboratory spectra and theoretical models of optically thin electron excited H2, with added Doppler-broadened Lyman Alpha emission. The observed Lyman Alpha emission wings extend more than 1 A from line center and appear correlated in strength with the H2 brightness. Individual rotational lines in the H2 Werner band system are resolved, allowing a determination of the H2 rotational temperature at the altitude of the emission. We derive best-fit temperatures from 400-450 to 700-750 K, with the auroral emission layer temperature changing either across the auroral oval or over several days' time. These observations demonstrate for the first time the ability to measure the observed rapid H2 temperature variations across Jupiter's auroral atmosphere.

Clarke, John T.↗