Cross sections and rate coefficients for excitation of the 2s(2)2p5(2)
P3/2-2s(2)2p5(2)P1/2 transition in fluorinelike Fe XVIII by proton (p)
, deuteron (d), triton (t), and alpha-particle (alpha) impact have bee
n calculated using the close-coupled impact-parameter method. These da
ta, in conjunction with R-matrix calculations of electron-impact excit
ation rates, are used to derive the theoretical emission line ratio R
= I(2s(2)2p5(2)P3/2-2s(2)2p5 2P1/2)/I(2s(2)2p5(2)2P3/2-2s2p6(2)S(1/2))
= I(974.8 angstrom)/I(93.4 angstrom) as a function of electron and he
avy-particle number density, and electron and ion temperature, for val
ues applicable to tokamak plasmas. A comparison of our results with ob
servations of R from the JIPP T-II-U tokamak at the Institute of Plasm
a Physics, Nagoya, Japan, for which the plasma parameters have been in
dependently determined, reveals excellent agreement between theory and
experiment, with discrepancies of typically less-than-or-equal-to 10%
. This provides observational support for the accuracy of the atomic d
ata adopted in the line ratio calculations.