Red Asymmetry Research Articles

A PHOTOELECTRIC HALPHA PROFILE FOR NOVA CYGNI 1975.

ABSTRACT A coude' photoelectric line scanner was used to obtain an Ha profile measurement for Nova Cygni on 1975 September 2/3. The line appears completely in emission with a flill half-width corresponding to 3600 km sec-1, and a definite red asymmetry. Key words: Nova Cygni - line profile - asymmetry

Effects of Thomson scattering on the shape of a spectral line

The effect of Thomson scattering and Compton effect on the shape of a spectral line is studied in the case of a plane-parallel atmosphere. The theoretical values of red shift and intensity at the top of the line, having an equivalent width 5√π10−10 cm, and of the red asymmetry are tabulated for 62 different values of the optical thickness τ′; from τ′=0.2/√3 to τ′=2.6/√3.

New aspects in the self-broadening of alkali resonance lines

In addition to previous absorption measurements of Cs resonance lines, new investigations on Na, K and Rb also showed definitely that beyond symmetrical Lorentzian central parts of the lines, the stronger components of the resonance lines have blue and the weaker components red asymmetry. This behaviour can be explained by a quasistatic treatment of the self-broadening mechanism taking interatomic interaction potentials into account. But with additional data it is now possible to give a different interpretation of the origin of observed asymmetries than suggested in the previous paper on Cs resonance lines (see abstr. A5740 of 1975). The asymmetries are shown to arise from the mutual repulsion of two potential curves of the same species.

Asymmetric self-broadening of Cs principal lines

16 lines of the principal series of Cs(62s1/2 to 7-162p3/2 and 62s1/2 to 7-122p1/2) were investigated in absorption. Cesium vapour density was varied from 1013 up to 1017 cm-3. Red asymmetries of all lines (extended red wings) were detected. This can be understood if electron transitions in the long-range interaction region follow the selection rules of molecules. It was established that the red and the blue wings of the lines each can be fitted to lorentzian profiles in small wavelength intervals. With the help of quasistatic theory the interaction constants from the long-range interaction potential Delta omega =C3/r3 multiplied by the oscillator strength were determined from measurements. For all lines the ratio of C3(red)/C3(blue) was found to equal 2 in accordance with earlier theoretical calculations. In the far line wing, deviation from a lorentzian profile occurs. This was interpreted as a consequence of electron transition in the short-range region of interatomic potentials.

The flares of August 1972

Observations of the August, 1972 flares at Big Bear and Tel Aviv, involving monochromatic movies, magnetograms, and spectra, are analyzed. The region (McMath 11976) showed inverted polarity from its inception on July 11; the great activity was due to extremely high shear and gradients in the magnetic field, as well as a constant invasion of one polarity into the opposite; observations in lambda 3835 show remarkable fast flashes in the impulsive flare of 18:38 UT on Aug. 2 with lifetimes of 5 sec, which may be due to dumping of particles in the lower chromosphere. Flare loops show evolutionary increases of their tilts to the neutral line in the flares of Aug. 4 and 7. Spectroscopic observations show red asymmetry and red shift of the H alpha emission in the flash phase of the Aug. 7 flare, as well as substantial velocity shear in the photosphere during the flare, somewhat like earthquake movement along a fault. Finally the total H alpha emission of the Aug. 7 flare could be measured accurately as about 2.5 x 10 to the 30th power erg, considerably less than coarser previous estimates for great flares.

The Shift and Broadening of the Resonance Doublet of BA II Caused by he and AR Collisions.

The frequency shifts and half-widths of the S/sup 2/-P/sup 2/ resonance doublet of Ba II have been observed in emission in the range of pressures from 400 to 1100 atm. and accompanying temperatures of 3300 to 5000 deg K. These conditions were generated by a rapid gas-compression technique, and the temperatures achieved were sufficient to vaporize Ba salts and to produce Ba ions whose radiation could be spectrographically detected. With He as the perturbing gas, the P/sup 2//sub 1/2/( lambda 4934) component shifted toward the violet, while the P/sup 2//sub 1/2/( lambda 4554) component remained unshifted; both lines exhibited symmetric intensity profiles. With Ar as the perturbing gas, both lines shifted toward the red, and both lines possessed marked red asymmetry. Qualitative agreement was noted between the behavior of these Ba II lines and the corresponding doublets of neutral alkali atoms perturbed by the same gases, but the form of the interaction potential between these excited ions and the rare-gas atoms could not be determined by application of existing theories of line broadening. (auth)

Resonance Broadening of Caesium

The resonance broadening of homogeneous Cs vapor in absorption was studied by means of the contour method. The intensities were obtained via the method of "astigmatic photometry" by utilizing the astigmatism of the Rowland grating. The pressure of the homogeneous absorbing vapor ranged from ${10}^{\ensuremath{-}2}$ to 17.5 mm Hg. The half breadth $\ensuremath{\gamma}$ varied rather linearly with the number of atoms per unit volume, with $(\frac{{\ensuremath{\gamma}}_{1}}{N})\ifmmode\times\else\texttimes\fi{}{10}^{7}=1.45$, $(\frac{{\ensuremath{\gamma}}_{2}}{N})\ifmmode\times\else\texttimes\fi{}{10}^{7}$ for the $^{2}P_{\frac{3}{2}}$ and $^{2}P_{\frac{1}{2}}$ eomponents of the resonance lines, respectively. The average value of the ratio of half breadths $\frac{{\ensuremath{\gamma}}_{1}}{{\ensuremath{\gamma}}_{2}}$ was found to be 1.8. The experimental half-width $\ensuremath{\gamma}$ is found to be about 1\textonehalf{} times larger than that predicted by W. V. Houston. Below pressures of 10 mm Hg the lines exhibited symmetrical broadening according to the "dispersion" formula. At higher pressures indications of a violet and red asymmetry are present for the $^{2}P_{\frac{3}{2}}$ and $^{2}P_{\frac{1}{2}}$ components, respectively. A definite band on the red side of the $^{2}P_{\frac{3}{2}}$ and one on the violet side of the $^{2}P_{\frac{1}{2}}$ was observed.

Broadening, Asymmetry and Shift of Rubidium Resonance Lines under Different Pressures of Helium and Argon up to 100 Atmospheres

A new absorption tube was constructed which made feasible the study of the pressure effects of foreign gases on the absorption lines of alkali vapors of homogeneous density and temperature. In addition to helium and argon at pressures up to 100 atmospheres, hydrogen was used up to 20 atmospheres. Up to relative density 46 the broadening is proportional to the concentration of helium or argon gas. The slopes of the half-width vs. relative density curves are 0.735 ${\mathrm{cm}}^{\ensuremath{-}1}$ and 0.594 ${\mathrm{cm}}^{\ensuremath{-}1}$ per unit relative density of helium for $^{2}P_{\frac{3}{2}}$ and $^{2}P_{\frac{1}{2}}$ components, respectively, and the corresponding values for argon are 0.855 ${\mathrm{cm}}^{\ensuremath{-}1}$ and 0.627 ${\mathrm{cm}}^{\ensuremath{-}1}$ per unit relative density. Helium produces a violet, argon a red asymmetry. The degree of asymmetry increases as the concentration of foreign gas increases, and is comparatively much greater for argon. For argon the asymmetry of the $^{2}P_{\frac{3}{2}}$ component is greater than that of the $^{2}P_{\frac{1}{2}}$ component, while for helium the reverse is true. Argon produces a greater shift than helium. The former produces a strong red shift, the latter a violet shift. For both gases the shift of the $^{2}P_{\frac{1}{2}}$ component is greater than that of the $^{2}P_{\frac{3}{2}}$ component. For helium the shift appears to be proportional to the relative density, and the shift of the longer wave-length component is about twice as great as that of the shorter wave-length component, while for argon the shifts for the doublet components are quite close, and the relation between shifts and relative densities obeys in general the 3/2 power relationship. Optical collision diameters as calculated from the half-width data are 13.37A and 7.753A for Rb---A and Rb---He, respectively. From the measurements of the amount of total absorption from the line contours, $f$ values and the transition probabilities were evaluated.

Pressure Effects of Rare Gases on the Second Doublet of Rubidium Principal Series

The displacement, asymmetry, and broadening of the second doublet of the rubidium principal series perturbed by pure helium, neon and argon up to 13 atmospheres are observed. The displacement as well as the broadening of the doublet components are not the same. The $^{2}P_{\frac{1}{2}}$ component shifts and broadens more conspicuously than the $^{2}P_{1\frac{1}{2}}$ component (an exception being the broadening by argon). The departure from linear relationship between the shift and the density of the perturbing gas is quite manifest. Both for helium and for neon the line contour shows a distinct asymmetry towards the violet, while for argon the line contour shows a very strong red asymmetry. For helium and neon the violet asymmetries of the $^{2}P_{\frac{1}{2}}$ component are stronger than that of the $^{2}P_{1\frac{1}{2}}$ component; the reverse is true for argon. The relationship between the half-width and the relative density is linear for foreign gas concentrations of relative densities up to 8 so far applied.