MEASUREMENTS OF THE SHIFT AND WIDTH OF SODIUM

MEASUREMENTS OF THE SHIFT AND WIDTH OF SODIUM n. S - 3 P TRANSITIONS IN HIGH PRESSURE SODIUM DISCHARGE Z. 1 Miokovic , D. Balkovic, D. Veza Physics Department, Faculty of Science, Uni-Zagreb, Bijenicka 32, HR-10002 Zagreb, Croatia (veza@phy. hr) 1 Faculty of Electrical Engineering, Uni-Osijek, K. Trpimira 2 B, 31000 Osijek, Croatia (zeljka@etfos. hr) MOTIVATION · Better and more complete understanding of physics and chemistry of high-pressure discharges (sodium-mercury (cadmium) and metal-halide discharges) ·The high-pressure discharge (sodium-cadmiumxenon) has been rarely investigated ·The line shift and the line broadening of higher members of n. D – 3 P (n > 4) series and n. S – 3 P (n = 5, 6, 7) series are rarely investigated ·To find out mechanisms leading to the formation of n. S-3 P (n = 5, 6, 7) sodium atomic line-profiles and to test or to determine the corresponding broadening mechanisms and the interaction constants ·Importance of atomic plasma parameters for modeling high-pressure discharges and optimization metal-halide and alkali lamps ·Comparison of the observed line shapes with the simulated line shape made within the Bartels’ method Fig. 1. Recently measured [3] Na 5 D-3 P and Na 6 D-3 P line shifts as a function of the electron density. The shifts show a linear dependence on the electron density. These shift-to-electron density data we used for determination of electron density by measurements of the line-shift in our Na-Cd and Na-Hg discharges. EXPERIMENT RESULTS Fig. 5. : An example of the measurements The 52 S 1/2 32 P 1/2; 3/2 atomic line measured from the 400 W Na-Cd discharge at the current of 3. 6 A (hollow circles). The theoretical profile (red line) represented by the best fit to the experimental data is calculated using the Bartels’ method [2] with the following plasma parameters: NNa = 2 1023 m-3, NCd = 22. 5 1023 m-3, de = 0. 031 nm, Ne = 2. 805 1021 m-3, we (HWHM) = 0. 0443 nm, and Te = 3850 K. The lower part shows the difference between experimental and calculated profiles. Fig. 2. Experimental arrangement: arrangement LPL- low pressure lamp; HPL-high pressure lamp; R- folding mirror; L-lens; F-cut of filter; M-monochromator; PMT-photomultiplier; A/D-analog-to-digital converter; PC-personal computer. Fig. 3. The external- or the line triggering for the time resolved measurements is used, provided by boxcar averager. All measurements were performed at the maximum value of the AC driving current. The electron density follows the sinusoidal variations of the discharge current over one period of driving voltage, whereas the density of neutral particles does not change. Fig. 6. The comparison of the measured line shift (de) and width (we) data with the results of the shift and width calculations by Griem (1964. , dotted line), Griem (1974. , dashed line) and Dimitrijevic (1985. , full line). CONCLUSIONS Fig. 4. The 52 D 3/2, 5/2 32 P 1/2; 3/2 atomic lines measured from the HP 400 W Na-Cd discharge at the current of 3. 4 A (hollow circles). The solid red line represents the best fit of Lorentzian profiles to the experimental data measured from the HP discharge. The lower part shows the same atomic lines measured from the low-pressure sodium spectral lamp (reference source, unshifted lines). • We measured the shape, the width and the shift of the sodium n 2 S 1/2 - 3 2 P 1/2, 3/2 (n = 5, 6, 7) transitions • Electron density determined measuring the shift of the sodium 6 D - 3 P and 5 D - 3 P transitions [3] • Electron temperature determined by Bartels’ method (fitting the calculated to the experimentally measured line shapes) • Line-shifts and widths of the sodium n. S - 3 P (n=5, 6, 7) and 4 D - 3 P transitions show an almost linear dependence on the electron density • Stark broadening is the dominant interaction mechanism References [1] [2] [3] [4] D. Azinovic, J. Rukavina, G. Pichler, D. Veza, FIZIKA, Vol. 22. , 469, (1989) H. Bartels, Z. Phys. , Vol. 128, 546 (1950) M. Kettlitz, P. Oltmanns, Phys. Rev. E, Vol. 54, No. 6, 6741 (1996) Z. Miokovic, D. Veza, FIZIKA A, Vol. 10. , 129, (2001)