EXCITATION CROSS-SECTION AND POLARIZATION OF THE CA-II LAMBDA = 393.3 NM LINE BY ELECTRON-IMPACT ON CA-I ATOMS

The optical excitation function and the polarisation of the Ca II lambda =393.3 nm (42P3/4 to 42S1/2) line following simultaneous ionisation and excitation from Ca I ground-state atoms have been measured using crossed electron and calcium atom beams. The absolute excitation cross section of the Ca II 2P3/2 state has been determined to be (0.72+or-0.27)*10-16 cm2 at an electron energy of 40 eV. The linear polarisation of the Ca II lambda =393.3 nm line has been measured from the 42P3/2 threshold to 200 eV. The polarisation was found to give a peak reading of 17% near threshold and to converge to zero at high energies.