CO/a/3/pi/ - Its production, detection, deactivation, and radiative lifetime
Deactivation and radiative lifetime of CO Cameron forbidden transition spectral bands produced by photon absorption
Black, G.↗
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Imaging of four planetary nebulae in the Magellanic Clouds using the Hubble Space Telescope Faint Object Camera
Using the Faint Object Camera on-board the Hubble Space Telescope, we have obtained images of four planetary nebulae (PNe) in the Magellanic Clouds, namely N2 and N5 in the SMC and N66 and N201 in the LMC. Each nebula was imaged through two narrow-band filters isolating forbidden O III 5007 and H-beta, for a nominal exposure time of 1000 s in each filter. In forbidden O III, SMC N5 shows a circular ring structure, with a peak-to-peak diameter of 0.26 arcsec and a FWHM of 0.35 arcsec while SMC N2 shows an elliptical ring structure with a peak-to-peak diameter of 0.26 x 0.21. The expansion ages corresponding to the observed structures in SMC N2 and N5 are of the order of 3000 yr. LMC N201 is very compact, with a FWHM of 0.2 arcsec in H-beta. The Type I PN LMC N66 is a multipolar nebula, with the brightest part having an extent of about 2 arcsec and with fainter structures extending over 4 arcsec.
Blades, J. C.↗
Narrow-band imaging and velocity maps of young stellar objects - Initial results
The first trials of a new technique, designed to map low-excitation ionized gas surrounding young stellar objects, are reported. The region surrounding the T Tau stars HL Tau and XZ Tau, that near HH 101, and that near IRS 5 in L1551 have been imaged through a narrow-band (4.7 A FWHM) forbidden S II filter; three-phase CCD chip was used as the detector. By tilting the narrow-band filter, it is possible to vary the wavelength of peak transmission and thus to detect high-velocity radial flows as well as map the morphology of the excited gas near these young stars. Evidence of an apparently helical outflow is found for HH 101. Redshifted gas appears to extend southward from HL Tau toward HH 30; a blueshifted jet extends northeastward of HL Tau. A series of forbidden S II knots is seen to extend along a jet directed southwestward from the infrared source IRS 5; the knot chain appears to delineate a blueshifted outflow that decelerates as it recedes from IRS 5.
Morgan, J. S.↗
Multispectrum Analysis of 12CH4 in the v4 Band: I. Air-Broadened Half Widths, Pressure-Induced Shifts, Temperature Dependences and Line Mixing
Lorentz air-broadened half widths, pressure-induced shifts and their temperature dependences have been measured for over 430 transitions (allowed and forbidden) in the v4 band of (CH4)-12 over the temperature range 210 to 314 K. A multispectrum non linear least squares fitting technique was used to simultaneously fit a large number of high-resolution (0.006 to 0.01/cm) absorption spectra of pure methane and mixtures of methane diluted with dry air. Line mixing was detected for pairs of A-, E-, and F-species transitions in the P- and R-branch manifolds and quantified using the off-diagonal relaxation matrix elements formalism. The measured parameters are compared to air- and N2-broadened values reported in the literature for the v4 and other bands. The dependence of the various spectral line parameters upon the tetrahedral symmetry species and rotational quantum numbers of the transitions is discussed. All data used in the present work were recorded using the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak.
Smith, MaryAnn H.↗
Line Assignments and Position Measurements in Several Weak CO2 Bands Between 4590/cm and 7930/cm
A substantial set of CO2 spectra from 4500 to 12000/cm has been obtained at Ames with 1500 m path length using a Bomem DA8 FTS. The signal/noise was improved compared to prior spectra obtained in this laboratory by including a filter wheel limiting the band-pass of each spectrum to several hundred per cm. We have measured positions of lines in several weak bands not previously resolved in laboratory spectra. Using our positions and assignments of lines of the Qbranch of the 31103-00001 vibrational band at 4591/cm, we have redetermined the rotational constants for the 31103f levels. Q-branch lines of this band were previously observed, but misassigned, in Venus spectra by Mandin. The current HITRAN values of the rotational constants for this level are incorrect due to the Q-branch misassignments. Our prior measurements of the 21122-00001 vibrational band at 7901/cm were limited to Q-and R-branch lines; with the improved signal/noise of these new spectra we have now measured lines in the weaker P branch. The 21122 (Gv = 790148/cm) levels are known to be perturbed by the 32211 (G(sub v) = 789757/cm) levels; new DND calculations predict that high-J lines of the forbidden 32211-00001 vibrational band 'borrow' intensity from the corresponding transitions of the 21122-00001 band. We have identified such Q- and R-branch transitions of the 32211-00001 band from 26 < J" < 44, based on our position measurements of lines in the 32211-02201 band at 6562/cm.
Giver, L. P.↗
Circumnuclear pileups of dust and gas in M82
Red H-alpha and R-band CCD images of the M82 galaxy were obtained and compared with corresponding NIR S III forbidden-line and I-band images and with a smaller Br-gamma infrared-array image of the central 500 pc. Results furnish evidence of circumnuclear pileup in M82, probably toroidal in form, which is dynamically linked to the central (bilobal) starburst and which is now collimating the subsequent eruptions and emergent radiation.
Waller, William H.↗
Electron excitation of the H2(a 3Sigma(g)(+) - b 3Sigma(u)(+)) continuum in the vacuum ultraviolet
The electron excitation function for the H2(a 3Sigma(g)(+) - b 3Sigma(u)(+)) continuum emission has been measured from 11 to 30 eV at 195.0 nm. The emission cross, section data have been combined with electron energy loss cross section measurements to extend the experimental data to 60 eV. The excitation cross section has been estimated by normalizing the data to the electron energy loss cross section at 20 eV and using a model to account for emission from the entire band system. The spin forbidden excitation of the a 3Sigma(g)(+) state is a major dissociative channel of H2 at low energy with a peak cross section of 1.7 +/- 0.85 x 10 exp -17 sq cm at 15.5 eV. The FWHM of the cross section is 7 eV. The high energy dependence of the cross section has a rapid 1/E-cubed fall off with electron energy, E, above 50 eV. A modified Born approximation analysis was applied to the data to provide an analytic model.
Ajello, J. M.↗
Transition moments, Franck-Condon factors, and lifetimes of forbidden transitions - Calculation of the intensity of the Cameron system of CO.
Discussion of the factors affecting the intensity of forbidden transitions in diatomic molecules. It is shown that using Franck-Condon factors to predict relative band intensities is less reliable for forbidden transitions than it is for allowed transitions. The intensity of the 0,0 and 1,0 bands of the a super 3 pi-super 1 sigma Cameron system of CO are calculated using perturbation theory. The intensity arises from spin-orbit mixing of the A super 1 pi state with the a super 3 pi state. From the known spin-orbit coupling constant of the a super 1 pi state and the known intensity of the fourth positive A super 1 pi-super 1 sigma transition, the oscillator strengths of the 0,0 and 1,0 bands are calculated to be 1.63 x 10 to the minus 7th power and 1.99 x 10 to the minus 7th power. Lifetimes of various rotational levels are shown to range from 2.9 to several hundred milliseconds.-
James, T. C.↗
The detection of the 5577.3 A forbidden line of O I in comets
The spectral synthesis of C2 Swan band sequence Delta V = -1 indicates the intensity of the forbidden green oxygen line of 5577.3 A to be about 3 to 5 percent of the 6300 A line. Therefore, it appears that the green line should be observable in high-resolution spectra of a bright comet. Festou and Feldman suggest red/green greater than or equal to 10 means a water parent origin.
Krishna Swamy, K. S.↗
An investigation of the optical constants and band gap of chromium disilicide
Optical properties of polycrystalline thin films of CrSi2 grown by the diffusion couple method on silicon substrates were investigated. An analysis of the energy dependence of the absorption coefficient indicates that the material is an indirect forbidden gap semiconductor with a band-gap value of slightly less than 0.35 eV. This result was confirmed by measurements of the temperature dependence of the intrinsic conductivity. The value of the bandgap corresponds well to an important window of transparency in the earth's atmosphere (3-5 microns), which makes the material of potential interest for IR detector applications.
Bost, M. C.↗
Reflectance spectroscopy of diogenite meteorite types from Antarctica and their relationship to asteroids
Measurements of the spectral reflectance (0.4-2.5 microns) of three diogenite meteorites found in Antarctica are examined. Comparisons are made with previous measurements of diogenites in order to correlate the mineralogy and petrography with the spectral characteristics that can also be measured on solar system objects of unknown composition. Even though the Antarctic diogenites have the same spectral characteristics as other diogenites, there are measurable differences between all diogenite spectra. Bands caused by spin-forbidden transitions of Fe(2+) ions in pyroxene, which are identified for the first time in reflectance spectra of powdered samples, are revealed in an analysis of the spectra into sums of Gaussian components. It is shown from these laboratory measurements that spectral reflectance measurements of asteroids and other solar system objects made with the visible CVF (circular variable filter) spectrometer used for laboratory measurements can provide useful information on their surface composition.
Mcfadden, L. A.↗
First results from the Faint Object Camera - SN 1987A
The first images of SN 1987A taken on day 1278 after outburst with the Faint Object Camera on board the Hubble Space Telescope are presented. The supernova is well detected and resolved spatially in three broadband ultraviolet exposures spanning the 1500-3800 A range and in a narrow-band image centered on the forbidden O III 5007 line. Simple uniform disk fits to the profiles of SN 1987A yield an average angular diameter of 170 + or - 30 mas, corresponding to an average expansion velocity of 6000 km/s. The derived broadband ultraviolet fluxes, when corrected for interstellar absorption, indicate a blue ultraviolet spectrum corresponding to a color temperature near 13,000 K.
Jakobsen, P.↗
CCD mosaic images of the supernova remnant 3C 400.2
We have constructed CCD mosaic images of the old Galactic supernova remnant 3C 400.2 in lines of H-alpha + forbidden N II, forbidden S II, and forbidden O III, plus a continuum band. These are the first CCD images covering the full extent of this remnant, and they reveal significantly more nebulosity than the deepest photographic plates. Comparison with radio and X-ray images indicates dramatically different morphology in the three regimes. The optical images both in H-alpha + forbidden N II and in forbidden S II show an almost complete, irregular shell of emission, with a diameter of about 16 arcmin, little over half that of the radio shell, while the X-ray structure is a centrally peaked ellipsoid. Approximate values for optical line fluxes are obtained; we estimate L(H-alpha) about 3 x 10 exp 35 ergs/s, roughly three times the X-ray luminosity. We also report a previously uncataloged planetary nebula southwest of 3C 400.2.
Winkler, P. F.↗
Measurement of Oxygen A Band Line Parameters by Using Modulation Spectroscopy with Higher Harmonic Detection
Wavelength modulation spectroscopy is used to demonstrate that extremely weak absorption lines can be measured even when these lines suffer from interference from the wings of adjacent stronger lines. It is shown that the use of detection at several harmonics allows such interference to be examined clearly and conveniently. The results of experimental measurements on a weak magnetic dipole driven, spin-forbidden line in the oxygen A band, which experiences interference from the wings of a pair of adjacent lines towards the blue and red regions of line center, are presented. A comparison of the experimental results to theory is given.
Dharamsi, Amin↗
Crystal field spectra of lunar pyroxenes.
Absorption spectra in the visible and near infrared regions have been obtained for pyroxene single crystals in rocks from the Apollo 11, 12, 14, and 15 missions. The polarized spectra are compared with those obtained from terrestrial calcic clinopyroxenes, subcalcic augites, pigeonites, and orthopyroxenes. The lunar pyroxenes contain several broad, intense absorption bands in the near infrared, the positions of which are related to bulk composition, Fe(2+) site occupancy and structure type of the pyroxene. The visible spectra contain several sharp, weak peaks mainly due to spin-forbidden transitions in Fe(2+). Additional weak bands in this region in Apollo 11 pyroxenes are attributed to Ti(3+) ions. Spectral features from Fe(3+), Mn(2+), Cr(3+), and Cr(2+) were not observed.
Burns, R. G.↗
Two-dimensional photometry of planetary nebulae
Monochromatic images of three planetary nebulae, NGC 6720, NGC 7662 and NGC 2392, were taken using narrow band interference filters centered on the forbidden emission lines of Oxygen I, II, III, Nitrogen II, Sulfur II and the permitted emission lines of Hydrogen I, Helium I and Helium II. The data was taken with a silicon intensified vidicon using the Palomar 1.5 meter telescope and was recorded digitally to an encoding level of 12 bits. The data was processed at the Image Processing Laboratory of the Jet Propulsion Laboratory. The calibrated images were used to investigate the three dimensional structure of the nebulae and to generate two-dimensional electron and temperature maps.
Kupferman, P. N.↗
HH 5, HH 6, and their exciting stars
Long-slit optical spectroscopy, astrometry, and H-alpha forbidden S II and broad-band 2 micron images of HH 5 and of the HH 6 complex have been obtained. The excitations and radial velocities of the individual HH knots are described. The morphology of the optical and the 2 micron images (the latter dominated by H2 emission and/or the continuum of any embedded exciting stars) is compared; and the new astrometry is discussed. Finally, the likely sources of excitation of these HH nebulae are commented on.
Cohen, Martin↗
Electric quadrupole transition in the a super 1 pi left-directed arrow x super 1 sigma super plus system of CO.
Electric quadrupole transition in fourth positive system of CO observed in bands of electric dipole allowed transition
FORBIDDEN TRANSITION↗