title: The 3C/3D line ratio in Ni XIX: New Ab Initio theory and experimental results.
abstract: We report a fully relativistic close-coupling calculation of the electron impact excitation of Ni xix to derive the 3C/3D line intensity ratio, with an uncertainty of 5%. Convergence of the calculation with respect to both channel coupling effects and the many interacting Rydberg series of resonances has been achieved. New measurements in an electron beam ion trap agree with our calculation. We show that the 3C/3D x-ray line ratio depends sensitively on both electron energy and beamwidth in an optically thin plasma. Accounting for this dependence improves the accuracy of the Ni abundance determination in astrophysical sources.
authors.affiliation: ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.
authors.forename: G X
authors.initials: GX
authors.lastname: Chen
authors.forename: K
authors.initials: K
authors.lastname: Kirby
authors.forename: E
authors.initials: E
authors.lastname: Silver
authors.forename: N S
authors.initials: NS
authors.lastname: Brickhouse
authors.forename: J D
authors.initials: JD
authors.lastname: Gillaspy
authors.forename: J N
authors.initials: JN
authors.lastname: Tan
authors.forename: J M
authors.initials: JM
authors.lastname: Pomeroy
authors.forename: J M
authors.initials: JM
authors.lastname: Laming