Papers by Amir Ahmad Saghiri
Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions With Materials and Atoms, 1999
Some recent new developments in dielectronic recombination (DR) measurements at heavy-ion storage... more Some recent new developments in dielectronic recombination (DR) measurements at heavy-ion storage rings are presented. A DR spectrum measured at CRYRING in Stockholm of F 6 is used to illustrate a few points regarding this kind of measurements. From the spectrum a transversal temperature of the adiabatically expanded electron beam of 3.0(5) meV is deduced, which is slightly higher than expected.
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 2000
Iron L-shell ions (Fe XVII to Fe XXIV) play an important role in determining the line emission an... more Iron L-shell ions (Fe XVII to Fe XXIV) play an important role in determining the line emission and thermal and ionization structures of photoionized gases. Existing uncertainties in the theoretical low temperature dielectronic recombination (DR) rate coefficients for these ions significantly affects our ability to model and interpret observations of photoionized plasmas. To help address this issue, we have initiated a laboratory program to produce reliable low temperature DR rates. Here, we present some of our recent results and discuss some of their astrophysical implications.
Physical Review Letters, 2000
New Century of X- …, 2001
Physical Review Letters, 2000
The low energy C IV dielectronic recombination (DR) rate coefficient associated with 2s→2p ∆n = 0... more The low energy C IV dielectronic recombination (DR) rate coefficient associated with 2s→2p ∆n = 0 excitations of this lithiumlike ion has been measured with high energy-resolution at the heavy-ion storage-ring tsr of the Max-Planck-Institut für Kernphysik in Heidelberg, Germany. The experimental procedure and especially the experimental detection probabilities for the high Rydberg states produced by the recombination of this ion are discussed in detail. From the experimental data a Maxwellian plasma rate coefficient is derived with ±15% systematic uncertainty and parameterized for ready use in plasma modeling codes. Our experimental result especially benchmarks the plasma rate coefficient below 10 4 K where DR occurs predominantly via C III(1s 2 2p4l) intermediate states and where existing theories differ by orders of magnitude. Furthermore, we find that the total dielectronic and radiative C IV recombination can be represented by the incoherent sum of our DR rate coefficient and the RR rate coefficient of Pequignot et al. (1991, Astron. Astrophys., 251, 680).
Uploads
Papers by Amir Ahmad Saghiri