TY - JOUR
T1 - Electron temperature and density dependence of E1 and E2 lines in the spectra of cobaltlike to potassiumlike ions
AU - Fournier, K. B.
AU - Goldstein, W. H.
AU - May, M.
AU - Finkenthal, M.
PY - 1996
Y1 - 1996
N2 - We report on a model for the intensity of “forbidden” 3[Formula Presented]-3[Formula Presented]4s electric quadrupole (E2) transitions in ions with ground states of the form 3[Formula Presented]3[Formula Presented] (k=1 through 9) across a broad range of temperatures and densities. (Molybdenum, Z=42, has been chosen as a representative element because of its role in magnetically confined fusion experiments and the availability of experimental data.) We make an identification of a 3[Formula Presented]-3[Formula Presented]4s E2 line in Mo XVII. In ions where strong E2 lines are not seen (ions with ground states 3[Formula Presented], 1≤k≤7), the suppression of the lines is explained by dipole decays to low-lying levels other than the ground state that become allowed through configuration interaction between 3[Formula Presented]4s states and excited states that have electric dipole (E1) decays to the 3[Formula Presented]3[Formula Presented] levels (and in like manner mixing between the 3[Formula Presented]3[Formula Presented] configuration and other configurations with E1 decays to the levels of 3[Formula Presented]4s). For k=8 and 9, we find that radiative cascades from high-lying levels play an important role in populating upper states of the E2 transitions. The role of direct, collisional ionization from valence and inner subshells of adjacent charge states in populating the upper states of 3d-4p E1 and 3d-4s E2 decays in Mo XVI and Mo XVII is found to be negligible. General agreement is found between observations of the E2 to E1 brightness ratio of Mo XVI made in a tokamak plasma and the predictions of the present model. Sensitivity to changes in electron density in the ratio of E2 to E1 decays can be used as a diagnostic for fusion plasmas.
AB - We report on a model for the intensity of “forbidden” 3[Formula Presented]-3[Formula Presented]4s electric quadrupole (E2) transitions in ions with ground states of the form 3[Formula Presented]3[Formula Presented] (k=1 through 9) across a broad range of temperatures and densities. (Molybdenum, Z=42, has been chosen as a representative element because of its role in magnetically confined fusion experiments and the availability of experimental data.) We make an identification of a 3[Formula Presented]-3[Formula Presented]4s E2 line in Mo XVII. In ions where strong E2 lines are not seen (ions with ground states 3[Formula Presented], 1≤k≤7), the suppression of the lines is explained by dipole decays to low-lying levels other than the ground state that become allowed through configuration interaction between 3[Formula Presented]4s states and excited states that have electric dipole (E1) decays to the 3[Formula Presented]3[Formula Presented] levels (and in like manner mixing between the 3[Formula Presented]3[Formula Presented] configuration and other configurations with E1 decays to the levels of 3[Formula Presented]4s). For k=8 and 9, we find that radiative cascades from high-lying levels play an important role in populating upper states of the E2 transitions. The role of direct, collisional ionization from valence and inner subshells of adjacent charge states in populating the upper states of 3d-4p E1 and 3d-4s E2 decays in Mo XVI and Mo XVII is found to be negligible. General agreement is found between observations of the E2 to E1 brightness ratio of Mo XVI made in a tokamak plasma and the predictions of the present model. Sensitivity to changes in electron density in the ratio of E2 to E1 decays can be used as a diagnostic for fusion plasmas.
UR - http://www.scopus.com/inward/record.url?scp=0009153746&partnerID=8YFLogxK
U2 - 10.1103/PhysRevA.53.709
DO - 10.1103/PhysRevA.53.709
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AN - SCOPUS:0009153746
SN - 1050-2947
VL - 53
SP - 709
EP - 716
JO - Physical Review A - Atomic, Molecular, and Optical Physics
JF - Physical Review A - Atomic, Molecular, and Optical Physics
IS - 2
ER -