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Usage of electron spectrometry
A) Studies of nuclear structure, decays and reactions
1) Study of conversion electrons 2) Study of electrons and positrons from beta decays 3) Study of Auger electrons 4) Determination of electron neutrino mass 5) Study of di-lepton pairs at high-energy physics
B) Application
1) Spectroskopy of electron energy losses with high resolution 2) Measurement of atomic level widths and binding energy of electrons 3) Study of molecular bonding from shifts of energies of conversion electron lines
Electron spectrum: 1) Continuous – from beta decay bremsstrahlung ... 2) Discrete – conversion, Auger electrons
Study of conversion coefficients
Common determination of gamma and electron intensities → determination of transition multipolarity
E0 transitions → are realized only by conversion electrons
Importance of correction on Doppler Shift (widening of line at spectrum)
Very often on beam measurement together with 4π detector systems for gammaray detection
Spectrum of conversion electrons - transition near yrast line
kinematic shift is described by Lorentz transformation:
*
*
** cos1
E
cpEE
•- coordinate system connected with moving nucleus
Compound nucleus → same velocityreaction and CE → different nucleus velocity
Determination of kinematics by nucleus detection
Study of electrons and positrons from beta decay
Measurement of Fermi-Kurie graph:
Schematic description of dependency Ne = f(Ee) in beta decay
Fermi graph for decay of tritium 3H, which is mostly used for neutrino mass determination
)E(Ekonst
EZ,F
ENeMAX
e
e
N(Ee) – number of electrons, F*(Z,Ee) – Fermi function, contains correction onCoulomb fields of nucleus and atomic electron cloud. mνc2 ≠ 0 → EMAX=Q - mνc2 Q – decay energy
Square of neutrino mass is determined
Necessity of very high resolution andMinimalization of energy loss possibilities(violation of spectrum shape)
Determination of neutrino mass
Present limit on neutrino mass (experiments at Mainz and Troick):
Experiment KATRIN
Integral electrostatic spectrometer
Determined limit for mν < 2-3 eV
Assumed sensitivity of spectrometer KATRIN
Scheme of spectrometer KATRIN
Complications: 1) Energy losses in target, molecule T2
2) Spectrometer stability
Obtained negative value of square mass
Usage of pair spectrometers for searching ofexotic particles decay
Some hypothetical particles should have decay channel to electron positron pair
Pair spectrometer APEX as example – it was not determined for axion searching
Vznikat by mohly například při srážkách těžkých iontů
Study of di-lepton pairs in high-energy physics
Sources of e+e- pairs:
Combinatorial background – its description is very important
Usage of track spectrometers
π+π- anihilation
Δ – Dalitz decay bremsstrahlung Decay of meson η
M(e+e-) [GeV/c2]
Au+Au1 GeV/n
combinato-rial background
η → e+e-
pn
10-10
10-8
10-6
0.4 0.8 1.2
φ→e+e-
ρ→ e+e-
ω→e+e-
Dilepton „cocktail“
CERES, NA50, HADES ...
Momentum resolution is very important
Spectroscopy of electron energy losses with high resolution
Set-up: 1) electron gun – electrons 2) electron spectrometer with high resolution
Electron gun EG3000 and electron spectrometer ELS5000 of LK Technologies company
Usage: 1) Surface studies by means of characteristic Auger electrons, electron scattering and diffraction 2) Structure studies
XPS method – X-ray photoelectron spectroscopy – surface, chemical analysis