| Accurate data for charge-changing processes are critical to the modeling of high-temperature plasmas as well as for guiding and benchmarking theoretical calculations. A completely new 90{dollar}spcirc{dollar} crossed-beams apparatus based on the "animated beams" technique has been developed at the university of Nevada, Reno to measure absolute ionization cross section of multiply charged ions. Beams of electrons and ions of well-defined energy are made to interact by sweeping the electron beam across the ion beam at right angles in a linear motion. The absolute ionization cross section {dollar}sigma{dollar} is determined from the equation: {dollar}sigma = Kqesp2nusb{lcub}e{rcub}nusb{lcub}i{rcub} {lcub}bf u{rcub} / ((nusb{lcub}e{rcub}sp2 + nusb{lcub}i{rcub}sp2)sp{lcub}1/2{rcub}Isb{lcub}e{rcub}Isb{lcub}i{rcub}){dollar}, in which all the required parameters are measured experimentally. K is the accumulated number of product ions, {dollar}Isb{lcub}e{rcub}{dollar} and {dollar}Isb{lcub}i{rcub}{dollar} are the total electric currents of the electrons and ions respectively, u is the sweep speed of the electron beam, {dollar}nusb{lcub}e{rcub}{dollar} and {dollar}nusb{lcub}i{rcub}{dollar} are the electron and ion velocities, q is the charge state of the ion. New experimental results are presented for the absolute electron-impact single and double ionization cross section as a function of electron energy for Mn{dollar}sp{lcub}9+{rcub}{dollar} (q = 5,6,7,8). The experimental data suggest that 3p-nl (n {dollar}ge{dollar} 4) excitation followed by autoionization for Mn{dollar}sp{lcub}5+{rcub}{dollar} and Mn{dollar}sp{lcub}6+{rcub}{dollar}, and 3s-nl (n {dollar}ge{dollar} 5) for Mn{dollar}sp{lcub}7+{rcub}{dollar} and Mn{dollar}sp{lcub}8+{rcub}{dollar} dominate the single ionization cross sections. The major mechanism for double ionization is attributed to single ionization of 2p and 2s L-shell electron followed by autoionization.; The next phase of the development of the experiment will involve measurement of the energies of the ejected electron, which will hopefully provide more information about the multiple ionization pathways. |
