Search NASA⌕ Search

SEARCH · Search NASA

Results for “MOLECULAR ROTATION”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Vibrational and rotational cooling of electrons by molecular hydrogen

It is noted that the cooling of electrons by vibrational and rotational excitation of molecular hydrogen plays an important role in the thermal balance of electrons in atmospheres containing significant amounts of H2. Calculations are described of vibrational and rotational cooling rates of electrons by H2. Results for a wide range of electron and neutral temperatures are presented, and analytical formulas for some to the cooling rates are given.

Waite, J. H., Jr.↗
NASA NTRS1989

Observations of the rotational transitions of OH from the Orion molecular cloud

A summary of observed rotationally excited, far infrared OH line emissions from Orion-KL made using the Kuiper Airborne Observatory is given, together with a list of the resulting publications, talks, and lectures based on this data. In addition, a paper is appended, particularly addressing the (16)OH and (18)OH emission from Orion-KL. The first detections of the (16)OH (2)pi(1/2) to (2)pi(3/2) J = 3/2(-) to 3/2(+) rotational cross-ladder transition (53.351 micrometer) and the (18)OH (2)pi(3/2) J = 5/2(+) to 3/2(-) rotational ground-state transition (120.1719 micrometer). It is found that both of these lines exhibit a P-Cygni profile.

Melnick, Gary J.↗
NASA NTRS1987

Giant-scale supernova remnants - The role of differential galactic rotation and the formation of molecular clouds

The evolution of remnants produced by the total supernova power from an evolved OB association in a differentially rotating galactic disk is presented. The calculations at 5 kpc and 10 kpc from the galactic center lead to column densities across the remnant shell, or across sections of the remnants, which eventually exceed the opacity criterion of Franco and Cox (1986) and thus form molecular clouds. The resultant clouds have masses larger than 100,000 solar masses, dimensions of several hundred parsecs, and a separation larger than 1 kpc. In contrast, at 20 kpc from the galactic center the opacity criterion is never fulfilled.

Tenorio-Tagle, G.↗
NASA NTRS1981

High spectral and spatial resolution observations of the 12.28 micron emission from H2 in the Orion molecular cloud

The pure rotational S(2) line of molecular hydrogen at 12.28 microns was looked for in 44 positions in the Orion moleular cloud with 6 in. beams and 35 km/s spectral resolution; it was detected in 27 positions. Emission was observed over a velocity range of + or - 100 km/s. The lines are approximately symmetric, and have full widths at half maximum ranging from 100 km/s down to the resolution limit. The distribution of intensities and line shapes is largely consistent with that seen in the 2 micron hydrogen transitions. However, unexpectedly complex line profiles and point-to-point variations in linear shapes appear, particularly in the region near IRc9.

Beck, S. C.↗
NASA NTRS1992

Mid-infrared rotational line emission from interstellar molecular hydrogen

The line emission from the v = 0-0 S(0), S(2), and S(3), and the v = 1-0 and v = 2-1 S(1) transitions of molecular hydrogen in clouds exposed to high FUV fluxes and in shocks is modeled. Particular attention is given to the lowest pure rotational H2 transitions at 20 and 17 microns, respectively. It is found that, in photodissociation regions (PDRs), the emission comes from warm (greater than about 100 k) molecular gas, situated at optical depths greater than about 1, beyond the hot atomic surface layer of the clouds. For FUV fields, G0 = 1000 to 100,000 times the average interstellar field densities n = 10 exp 3 - 10 exp 7/cu cm, the typical line intensities are in the range 10 exp -6 to 10 exp -4 ergs/s sq cm sr. The predictions for the line intensities from both C-type and J-type shock models are compared. The results are applied to recent observations of the 0-0 S(1) transition in both the PDR and the shocked gas in Orion.

Burton, Michael G.↗
NASA NTRS1975

Conversion of laser energy to gas kinetic energy

Techniques for the gas phase absorption of laser radiation for conversion to gas kinetic energy are discussed. Absorption by inverse Bremsstrahlung, in which laser energy is converted at a gas kinetic rate in a spectrally continuous process, is briefly described, and absorption by molecular vibrational rotation bands is discussed at length. High pressure absorption is proposed as a means of minimizing gas bleaching and dissociation, the major disadvantages of the molecular absorption process. A band model is presented for predicting the molecular absorption spectra in the high pressure absorption region and is applied to the CO molecule. Use of a rare gas seeded with Fe(CO)5 for converting vibrational modes to translation modes is described.

Caledonia, G. E.↗
NASA NTRS1976

Hydrogen molecules in interstellar space

The most important results obtained from Copernicus satellite observations of ultraviolet H2 absorption features are summarized. The properties of the hydrogen molecule are described along with the radiative processes in which it can be involved. Techniques and equipment used in observing H2 absorption features from space are reviewed. The results are discussed in terms of the fraction of hydrogen in molecular form, rotational excitation of H2, physical conditions within interstellar gas clouds, and approaching clouds characterized by high excitation and negative radial velocity. It is shown that: (1) an appreciable fraction of the hydrogen in denser and thicker clouds is molecular, (2) at least some of the interstellar clouds are far from pressure equilibrium, (3) the approaching clouds are apparently dense thick sheets moving toward the sun as viewed in the local standard of rest, (4) these clouds are probably shock waves produced in the interstellar gas by old supernova remnants or expanding H II regions, and (5) the abundances relative to H of such elements as O, Mg, Si, and Cl in these clouds are nearly equal to the solar values, which is in contrast to the depletions observed in many other interstellar clouds.

Spitzer, L.↗
NASA NTRS1987

Bipolar flows, molecular gas disks, and the collapse and accretion of rotating interstellar clouds

Rigorous numerical models of the collapse and accretion of rotating, axisymmetric, isothermal interstellar clouds are studied. The results show that molecular gas disks and evacuated bipolar cavities both appear to be natural consequences of the collapse of rotating interstellar clouds. Dynamically significant magnetic fields may not be necessary for explaining either phenomenon. The models strongly support theoretical models of the type where an isotropic wind from a pre-main sequence star is extrinsically collimated by a rotationally derived molecular gas cloud. The models imply that collimation should be strongest on small scales where rotational effects are most important, i.e., in the dense region of the molecular gas disk.

Boss, Alan P.↗
NASA NTRS1978

Collisional excitation of interstellar molecules - H2

Cross sections for the important rotational transitions in molecular hydrogen collisions are presented for rotational levels to j = 11 and energies to 20,000 K. These have been obtained from extensive theoretical calculations. The resulting cross sections are fitted to a simple polynomial in the energy, and the coefficients are tabulated for easy utilization.

Green, S.↗
NASA NTRS1990

MHD shocks in the ISM

Researchers survey shock solutions of a partially ionized gas with a magnetic field. The gas is modeled by interacting neutral, ion, electron and charged grain components. They employ a small neutral-ion chemical network to follow the dissociation and ionization of the major species. Cooling by molecular hydrogen (rotational, vibrational and dissociation), grains and dipole molecules is included. There are three basic types of solutions (C, C asterisk, and J) and some more complicated flows involving combinations of the basic types. The initial preshock conditions cover hydrogen nuclei densities of 1 less than n less than 10(exp 10) cm(-3) and shock velocities of 5 less than v(sub s) less than 60 km/s. The magnetic field is varied over 5 decades and the sensitivity of the results to grain parameters, UV and cosmic ray fluxes is ascertained. The parameter space is quite complicated, but there exist some simple divisions. When the initial ionization fraction is small (chi sub i less than 10(-5)), there is a sharp transition between fully C solutions at low velocity and strong J solutions at high velocity. When the initial ionization fraction is larger, C asterisk and/or very weak J shocks are present at low velocities in addition to the C solutions. The flow again changes to strong J shocks at high velocities. When the ionization fraction is large and the flow is only slightly greater than the bulk Alfven velocity, there is a complicated mixture of C, C asterisk and J solutions.

Chernoff, D. F.↗