Electron transfer from H2 and Ar to stored multiply charged argon ions produced by synchrotron radiation

The rate coefficients for electron transfer from Ar and H2 to Arq+ ions (3≤q≤6) have been measured using an ion-storage technique in a Penning ion trap. The ions were produced in the trap by K-shell photoionization of Ar atoms, using broadband synchrotron x-ray radiation. K-electron removal resulted in vacancy cascading, yielding a distribution of argon-ion charge states peaked near Ar4+. The stored ion gas had an initial temperature near 480 K. The basic data determining the rate coefficients k(Arq+) are the storage time constants of each charge state in the trap, in the presence of a measured pressure of target gas. The results of the measurements (in units of 10-9 cm3 s-1) are k(Ar3+,H2)=4.3(0.7), k(Ar3+,Ar)=1.6(0.2), k(Ar4+,H2)=5.2(0.6), k(Ar4+,Ar)=2.5(0.3), k(Ar5+,H2)=5.9(0.7), k(Ar5+,Ar)=2.9(0.3), k(Ar6+,H2)=8.5(1.2), and k(Ar6+,Ar)=2.5(0.3)