Decrease In Intensity Of Lines Research Articles

Decrease in Intensity of Hg Lines near the Source in Weakly Ionized Mercury Gas Flow

In a flowing mercury afterglow with d. c. discharge source, rapid decrease in intensity of Hg lines near the source are investigated. Both the axial intensity distribution along the flow downstream and the radial one are interpreted in connection with diffusion of electron to the wall and electron to the wall and electron attachment. The effective diffusion coefficient is found to be D β,γ =2.7×10 3 / p (cm 2 /sec), which is close to the ambipolar diffusion coefficient under the experimental conditions i. e. n e =5×10 8 /cm 3 and T e =2 eV. As for the resonance line (6 3 P 1 –6 1 S 0 ), slow decrease in intensity as compared with decrease in intensity of lines emitted from the higher levels is taken to be due to the radiative imprisonment and in consequence the absorption coefficient of this line is obtained as 1.2×10 -13 n 0 /cm and the quenching cross section of the state 6 3 P 1 due to the collisions with mercury atoms as 10 =0.048 A 2 .

Nuclear Magnetic Resonance of Ti in Ti–H Systems

The nuclear magnetic resonance spectrum of 47,49Ti in powder samples of metallic titanium hydride TiHx has been studied over the range of hydrogen concentrations corresponding to 1.7 ≤ x ≤ 2.0. For TiH2 the Knight shift is found to be +0.26 ± 0.04%, and there is no change in the Knight shift as a function of hydrogen concentration over the range studied. The titanium resonance in all samples was quite broad, 20 Oe, so that the lines from the two isotopes were not resolved. As a function of hydrogen concentration, the line shape was found to remain constant, but a rapid decrease of line intensity was noted. In order to investigate the possibility of magnetic ordering suggested by earlier studies of the magnetic susceptibility of TiH2, studies of the magnetic-field dependence and temperature dependence of the resonance were also performed. No dependence of Knight shift or line shape on magnetic field was observed over the range 9.0–15.0 kOe. No changes in Knight shift or line shape were observed in the temperature region 170°–525°K, thoroughly encompassing the region of the magnetic susceptibility maximum at approximately 300°K. These results strongly suggest that the cause of the maximum in the magnetic susceptibility is not magnetic ordering. Results on hydrogen and deuterium resonances in these samples are also reported.

Behaviour of the First Balmer Lines in a High Density Plasma†

Observation of Balmer line profiles revealed their relative constriction and growing asymmetry with increasing ion density, measured in the range of 2 × 1016 to 3 × 1017 ion/cm3. The fit of these profiles with the existing theoretical profiles gives smaller densities by the use of higher series members and smaller densities by the use of a red wing as compared with that of a violet wing. The phenomenon is believed to be caused by a combined action of the transition from the impact to the quasi-static line broadening effect of electrons and of the dissolution (pre-ionization) of discrete energy levels. The change in the line broadening mechanism due to the electrons makes the line narrower than in the case in which there would be no such change, because the quasi-static broadening does not rise so steeply with density as the impact broadening. The dissolution effect on the other hand, is accompanied by a decrease in line intensity and in asymmetry, the red wing being narrower than the violet one. The disso...