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A computer program is given for calculating the rotational Raman spectrum for molecular nitrogen and oxygen. Provision is made for pressure broadening. Several sample calculations at various pressures are shown. The relative heights of some of the lines are affected by pressure broadening.
H-2NMR is introduced as a tool for investigating slow molecular motion in the glass transition region of amorphous polymers. In particular, we compare H-2 spin alignment echo spectra of chain deuterated polystyrene with model calculations for restricted rotational Brownian motion. Molecular motion in the polyztyrene-toluene system has been investigated by analyzing H-2NMR of partially deuterated polystyrene and toluene, respectively. The diluent mobility in the mixed glass has been decomposed into solid and liquid components where the respective average correlation times differ by more than 5 decades.
A system was developed and applied at the NASA Manned Spacecraft Center for measuring and analyzing directional molecular flows in a large thermal vacuum chamber in order to verify molecular environment and identify characteristic and abnormal test article and chamber conditions. The system is described, and some results obtained in over 1200 hours of operation are given.
The problem of absorption of microwaves by molecular oxygen in the atmosphere is treated by means of a first-order approximation to the impact theory of overlapping spectral lines. By including only the coupling between adjacent rotational states in molecular collisions, we have devised a simple approximate method for computing the interference between lines from measurements on the resolved lines. The need for an empirically determined function describing the linewidth/pressure ratio is eliminated. Comparisons with measurements at atmospheric pressures show that the first-order interference accounts for the low absorption at the band wings near 1 atm pressure. It also predicts the correct amount of asymmetry between high and low frequency wings.
The goal of the observations carried out under this grant was to use several transitions of OH to infer conditions within a 1-arcminute region centered on Orion-KL. OH was selected as a diagnostic because: (1) it was predicted to be sufficiently abundant to be detectable by the KAO spectrometers; (2) there exist a number of transitions in the far- infrared free from atmospheric interference at airplane altitudes; and (3) these transitions are sensitive to a range of collisional and radiative excitation conditions believed to apply toward Orion-KL These observations were carried out as a Guest Investigator in collaboration with the Townes and Houck spectrometer groups. Though not every flight series resulted in usable data -due to technical difficulties with instrumentation - sufficient data was obtained to yield a clear picture of the source of the OH emission in Orion-KL.
Emission spectroscopy measurements were made of the plasma flow inside the nozzle of a 1 kW class arcjet thruster. The thruster propellant was a hydrogen-nitrogen mixture used to simulate fully decomposed hydrazine. The 0.25 mm diameter holes were drilled into the diverging section of the tungsten thruster nozzle to provide optical access to the internal flow. Atomic electron excitation, vibrational, and rotational temperatures were determined for the expanding plasma using relative line intensity techniques. The atomic excitation temperatures decreased from 18,000K at a location 3 mm downstream of the constrictor to 9,000K at a location 9 mm from the constrictor, while the molecular vibrational and rotational temperatures decreased from 6,500K to 2,500K and from 8,000K to 3,000K, respectively, between the same locations. The electron density measured using hydrogen H line Stark broadening decreased from about 10(exp 15) cm(-3) to about 2 times 10(exp 14) cm(-3) during the expansion. The results show that the plasma is highly nonequilibrium throughout the nozzle, with most relaxation times equal or exceeding the particle residence time.
Emission spectroscopy measurements were made of the plasma flow inside the nozzle of a 1-kW-class arcjet thruster. The thruster propellant was a hydrogen-nitrogen mixture used to simulate fully decomposed hydrazine. Atomic electron-excitation, vibrational, and rotational temperatures were determined for the expanding plasma using relative line intensity techniques. The atomic excitation temperature decreased from 18,000 K at a location 3 mm downstream of the constrictor to 9000 K at a location 9 mm from the constrictor, while the molecular vibrational and rotational temperatures decreased from 6500 K to 2500 K and from 8000 K to 3000 K, respectively, between the same locations. The electron density, measured using hydrogen H-beta line Stark broadening, decreased from about 10 to the 15th cu cm to about 2 x 10 to the 14th cu cm during the expansion. The results show that the plasma is highly nonequilibrium throughout the nozzle, with most relaxation times equal or exceeding the particle residence time.
Approximation of forces and momenta acting on axisymmetric bodies rotating in free-molecular stream and in luminous flux
Aperture synthesis and large-scale CO observations of NGC 3079 are reported which reveal several striking features in the molecular cloud distribution of this galaxy. The CO emission in the center of the galaxy is localized in a disk which is 660 pc in radius and which contains 5.7 x 10 to the 9th solar masses of molecular gas. The kinematics of the molecular clouds suggest rotation, and the H2 accounts for about 20 percent of the dynamical mass in this region. The CO and 5 GHz radio continuum peaks coincide spatially, indicating that the CO emission is coincident with the galactic nucleus. The H-alpha shell near the center of the galaxy is adjacent to the molecular disk. The H2 surface densities in the galaxy range over three orders of magnitude, decreasing from 1000 solar masses/sq pc in the center to less than 2 solar masses/sq pc at R greater than 10 kpc.
Rate coefficients for the reactive processes of ortho-para conversion in which the j = 0 rotational level of molecular hydrogen is excited to the j = 1 and j = 3 level by impacts with hydrogen atoms are calculated for temperatures between 30 K and 1000 K using a fully converged complete close-coupled method. Rate coefficients are also obtained for the excitation from the j = 0 to the j = 2 rotational level and from the j = 1 to the j = 3 rotational level. The interference between the direct and reactive channels is taken into account as is the geometric phase resulting from the adiabatic separation of electronic and nuclear motion that generates the potential energy surface. Convenient analytic representations of the rate coefficients are presented.
Ground-state rotational parameters for molecular hydrogen are evaluated using a combination of laboratory and observational data. High-accuracy v = 0 - 0 S(0)-S(5) frequencies from infrared laboratory measurements are analyzed simultaneously with available observed frequencies for the S(8), S(9), S(12), S(13), S(14), and S(15) Orion emission lines. The laboratory and Orion measurements are consistent with each other within their measurement errors. The combined data set yields a determination of five v = 0 rotational parameters and an improvement in the high-J calculated line positions. The analysis produces the parameters (in per cm): B(0) = 59.334627(30), D(0) = 0.0456912(30), H(0) = 4.8974(90) x 10 to the -5th, L(0) = -6.320(110) x 10 to the -8th, M(0) = 7.19(30) x 10 to the -11th, where a correction is made for the estimated contribution of sixth and higher orders.
Pressure-narrowing theory applied to calculating equivalent widths of lines in quadrupole rotation- vibration spectrum of molecular hydrogen
Circumstellar accretion disks transfer matter from molecular clouds to young stars and to the sites of planet formation. The disks observed around pre-main-sequence stars have properties consistent with those expected for the pre-solar nebula from which our own Solar System formed 4.5 Gyr ago. But the 'debris' disks that encircle more than 15% of nearby main-sequence stars appear to have very small amounts of gas, based on observations of the tracer molecule carbon monoxide: these observations have yielded gas/dust ratios much less than 0.1, whereas the interstellar value is about 100 (ref. 9). Here we report observations of the lowest rotational transitions of molecular hydrogen (H2) that reveal large quantities of gas in the debris disks around the stars beta Pictoris, 49 Ceti and HD135344. The gas masses calculated from the data are several hundreds to a thousand times greater than those estimated from the CO observations, and yield gas/dust ratios of the same order as the interstellar value.
A semiempirical molecular-orbital method for modelling the effective potential for electron-molecule scattering is applied to elastic scattering and rotational excitation of CO2 at 20 eV impact energy. Agreement with experiment is reasonably good. The calculated rotationally summed integral cross section is 67.8 a sub 0 squared.
Electron energy loss rate for D region determined by Maxwellian velocity distribution of thermal component brought about by collisions with molecular nitrogen involving rotational transition
Distorted wave calculation from rotational excitation of molecular hydrogen and molecular deuterium in thermal collisions with atomic hydrogen, presenting angular distributions, cross sections, etc
Spectroscopic electron beam diagnostic technique, examining negligible effect elevated vibrational temperatures have on measured rotational temperatures of molecular nitrogen
Diatomic Br molecular vibration-rotation coupling effects on energy transfer during Br-Ar collisions, determining probability distributions