Pionic deuterium Strauch, Th; Amaro, F. D.; Anagnostopoulos, D. F. ...
The European physical journal. A, Hadrons and nuclei,
07/2011, Letnik:
47, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The strong-interaction shift
ε
1
s
π
D
and broadening
Γ
1
s
π
D
in pionic deuterium have been determined in a high statistics study of the
π
D(3
p
-1
s
) X-ray transition using a high-resolution ...crystal spectrometer. The pionic deuterium shift will provide constraints for the pion-nucleon isospin scattering lengths extracted from measurements of shift and broadening in pionic hydrogen. The hadronic broadening is related to pion absorption and production at threshold. The results are
ε
1
s
π
D
= (−2356 ± 31) meV (repulsive) and
Γ
1
s
π
D
meV yielding for the complex
π
D scattering length
a
π
D
= −(24.99±0.33)+
i
(6.22
−0.26
+0.12
) × 10
−3
m
π
−1
. From the imaginary part, the threshold parameter for pion production is obtained to be
α
= (251
−11
+5
)
μ
b. This allows, in addition, and by using results from pion absorption in
3
He at threshold, the determination of the effective couplings
g
0
and
g
1
for
s
-wave pion absorption on isoscalar and isovector
NN
pairs.
Analytical study of electrostatic ion beam traps Vallette, Alexandre; Indelicato, P.
Physical review special topics. PRST-AB. Accelerators and beams,
11/2010, Letnik:
13, Številka:
11
Journal Article
Recenzirano
Odprti dostop
The use of electrostatic ion beam traps requires one to set many potentials on the electrodes (ten in our case), making the tuning much more difficult than with quadrupole traps. In order to obtain ...the best trapping conditions, an analytical formula giving the electrostatic potential inside the trap is required. In this paper, we present a general method to calculate the analytical expression of the electrostatic potential in any axisymmetric set of electrodes. We use conformal mapping to simplify the geometry of the boundary. The calculation is then performed in a space of simple geometry. We show that this method, providing good accuracy, allows one to obtain the potential on the axis as an analytic function of the potentials applied to the electrodes, thus leading to fast, accurate, and efficient calculations. We conclude by presenting stability maps depending on the potentials that enabled us to find the good trapping conditions for O4+ at much higher energies than what has been achieved until now.
We plan to measure several 2S-2P transition frequencies in mu He-4(+) and mu He-3(+) by means of laser spectroscopy with an accuracy of 50 ppm. This will lead to a determination of the corresponding ...nuclear rms charge radii with a relative accuracy of 3 x 10(-4), limited by the uncertainty of the nuclear polarization contribution. First, these measurements will help to solve the proton radius puzzle. Second, these very precise nuclear radii are benchmarks for ab initio few-nucleon theories and potentials. Finally when combined with an ongoing measurement of the 1S-2S transition in He+, these measurements will lead to an enhanced bound-state QED test of the 1S Lamb shift in He+.
We report on measurements of the Kβ diagram, valence‐to‐core (VtC), and hypersatellite X‐ray spectra induced in metallic Cr by photon single and double K‐shell ionization. The experiment was carried ...out at the Stanford Synchrotron Radiation Lightsource using the seven‐crystal Johann‐type hard X‐ray spectrometer of the beamline 6‐2. For the Kβ diagram and VtC transitions, the present study confirms the line shape features observed in previous works, whereas the Khβ hypersatellite transition was found to exhibit a complex spectral line shape and a characteristic low‐energy shoulder. The energy shift of the hypersatellite relative to the parent diagram line was deduced from the measurements and compared with the result of extensive multiconfiguration Dirac–Fock (MCDF) calculations. A very good agreement between experiment and theory was found. The MCDF calculations were also used to compute the theoretical line shape of the hypersatellite. A satisfactory agreement was obtained between the overall shapes of the experimental and theoretical spectra, but deviations were observed on the low‐ and high‐energy flanks of the hypersatellite line. The discrepancies were explained by chemical effects, which were not considered in the MCDF calculations performed for isolated atoms.
Spectra emitted by highly ionized tungsten atoms from magnetically confined plasmas show a common feature: a narrow structured quasi-continuum emission band most prominent in the range 4−7 nm, which ...accounts for 40−80% of the radiated power. This band has been fairly well explained by unresolved transitions from groups 4
d
-4
p
, 4
f
-4
d
(
Δn
= 0) and 5
d
-4
f
, 5
g
-4
f
and 5
p
-4
d
(
Δn
= 1). In this work we use a Multi-Configuration Dirac-Fock code in Breit self-consistent field mode to compute level energies and transition probabilities for W
27+
to W
37+
ions contributing to this emission band. Intra-shell correlation was introduced in the calculation for both initial and final states and all dipole and quadrupole radiative transitions have been considered. The wavefunctions in the initial and final states are optimized separately and the resulting non-orthogonality effect is fully taken into account. The importance of some satellite lines was assessed. Together with the ionic distributions obtained by using the FLYCHK application and assuming that the initial states population depends statistically on the temperature we were able to synthesize plasma emission spectrum profiles for several electron temperatures.
We provide, for the first time to our knowledge, accurate theoretical data for the the transition energy and probability values related to the decay of the most important excited states in He- ...through C-like lanthanum and cerium ions leading to the emission of
K
X-ray lines. We employed the multiconfiguration Dirac-Fock method, including QED corrections, to obtain the wave functions and energy values of each level involved in the X-ray analyzed transitions. The presented data may be used, among others, in the diagnostic of laboratory plasmas, such as the ones obtained in EBIT and ECRIS sources.
In this paper, we present an experimental and theoretical study of excitation processes for the heaviest stable helium-like ion, that is, He-like uranium occurring in relativistic collisions with ...hydrogen and argon targets. In particular, we concentrate on angular distributions of the characteristic Kα radiation following the K → L excitation of He-like uranium. We pay special attention to the magnetic sub-level population of the excited 1s2lj states, which is directly related to the angular distribution of the characteristic Kα radiation. We show that the experimental data can be well described by calculations taking into account the excitation by the target nucleus as well as by the target electrons. Moreover, we demonstrate for the first time an important influence of the electron-impact excitation process on the angular distributions of the Kα radiation produced by excitation of He-like uranium in collisions with different targets.
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