الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
 |  | from | 125 |  |  |
| | | from | 125 | | |
Abstract
A crossed-beam apparatus was built to investigate the optical excitation function and the polarisation of the Hel linesX * 5016 % (31P-► 21S) and X = 4922 % (4*D -> 2*Pexcited by electron impact . The measurements were carried out in the energy range from threshold to 200 eV The measured data, for the excitation function of the Helo 1 i line X = 5016 A (3 P-> 2 S) showed a slow rise of the
excitation function curve to a broad maximum at energyZ 100 eV . In case of the Hel line X = 4922 % (4 D-> 21p)<the shape of the excitation function curve showed a steep rise>from threshold to a maximum at % 50 eV , then it decreased<rather quickly with increasing the electron energy The polarisation measurements of the Hel X = 5016 2 asa function of the incident electron energy showed a thresholdvalue of 59 % and a linear fall off towards zero value as theelectron energy was increased . For the Hel line \ * 4922 %. ,
the polarisation curve showed a characteristic maximum of 46 ifr
at 34 eV ana a steep fall off as the threshold is approached .
\At high energy , the decrease in polarisation with increasing
tthe incident electron energy was almost linear with a trend of
reaching zero value at energy above 200 eV .
The present measurements for the optical excitation function and polarisation are compared with the previoustheoretical and experimental data . The agreement between thepresent data and the previous published work is very good andprove the accuracy of our photon detector channel forfuture polarisation measurements .ii.