Photons in the universe
Photons in the universe
Element production on the sun
Spectral lines of hydrogen absorption spectrum absorption hydrogen gas
Hydrogen emission spectrum Element production on the sun wave length nm 5
Spectral analysis H Spectral analysis Kirchhoff und Bunsen: Every element has a characteristic emission band Max Planck 6
Nuclear Resonance Fluorescence Nuclear Resonance Fluorescence (NRF) is analogous to atomic resonance fluorescence but depends upon the number of protons AND the number of neutrons in the nucleus
Photon-nuclear reactions with MeV γ-rays pure electromagnetic interaction spin selectivity (mainly E1, M1, E2 transitions) γ-ray
Photon-nuclear reactions with MeV γ-rays pure electromagnetic interaction spin selectivity (mainly E1, M1, E2 transitions) γ-ray
Low energy photon scattering at S-DALINAC white photon spectrum wide energy region examined
Absorption processes
Principle of measurement and self absorption
First γγ-coincidences in a γ-beam
First γγ-coincidences in a γ-beam
First γγ-coincidences in a γ-beam
Total power received by Earth from the Sun 174 Peta (10 15 ) Watt @ extreme light infrastructure, Europe
Compton scattering and inverse Compton scattering Compton scattering: Elastic scattering of a high-energy γ-ray on a free electron. A fraction of the γ-ray energy is transferred to the electron. The wave length of the scattered γ-ray is increased: λ > λ. hνν mm ee cc 2 λλ λλ = h mm ee cc 1 ccccccθθ γγ EE γγ = EE γγ 1 + EE γγ mm ee cc 2 1 cccccccc Inverse Compton scattering: Scattering of low energy photons on ultra-relativistic electrons. Kinetic energy is transferred from the electron to the photon. The wave length of the scattered γ-ray is decreased: λ < λ. λλ λλ 1 ββ ccccccθθ γγ 1 + ββ ccccccθθ LL
Inverse Compton scattering Electron is moving at relativistic velocity Transformation from laboratory frame to reference frame of e - (rest frame): in order to repeat the derivation for Compton scattering EE γγ = γγ EE γγ 1 vv cc ccccccθθ ee γγ Lorentz factor: γγ = 1 ββ 2 1/2 = 1 + TT ee MMMMMM 931.5 0.00055 Doppler shift EE γγ = EE γγ 1 + EE γγ mm ee cc 2 1 ccccccφφ Compton scattering in rest frame EE γγ = γγ EE γγ 1 + vv cc ccccccθθ ee γγ transformation into the laboratory frame Limit EE γγ mm ee cc 2 EE γγ γγ 2 EE γγ 1 vv cc ccccccθθ ee γγ 1 + vv cc ccccccθθ ee γγ EE γγ 4γγ 2 EE γγ electron and γ interaction θθ ee γγ~180 0 γ emission relative to electron θθ ee γγ ~00
Laser Compton backscattering Energy momentum conservation yields ~4γγ 2 Doppler upshift Thomsons scattering cross section is very small (6 10-25 cm 2 ) High photon and electron density are required
Gamma rays resulting after inverse Compton scattering photon scattering on relativistic electrons (γ >> 1) hνν = 2.3 ev 515 nnnn TT ee llllll = 720 MMMMMM γγ ee = 1 + TT ee llllll MMMMMM 931.5 AA ee uu = 1410 EE γγ = 2γγ ee 2 1 + ccccccθθ LL 1 + γγ ee θθ γγ 2 + aa0 2 + 4γγ eeee LL mmcc 2 EE LL 4γγ ee EE LL mmcc 2 aa LL = = recoil parameter eeee mmωω LL cc = normalized potential vector of the laser field E = laser electric field strength EE LL = ħωω LL γγ ee = EE ee = 1 = Lorentz factor mmcc 2 1 ββ2 maximum frequency amplification: head-on collision (θ L = 0 0 ) & backscattering (θ γ = 0 0 ) A. H. Compton Nobel Prize 1927 EE γγ ~4γγ ee 2 EE LL 18.3 MMMMMM
Scattered photons in collision Yb: Yag J-class laser 10 Peta (10 15 ) Watt QQ = 1 nnnn UU LL = 0.5 JJ hνν LL = 2.4 eeee = 3.86 10 19 JJ 515 nnnn NN ee = 6.25 10 9 NN LL = 1.3 10 18 Luminosity: LL = NN LL NN ee 4ππ σσ RR 2 ff 2.9 10 32 ff cccc 2 ss 1 σσ RR = 15 μμμμ γ-ray rate: NN γγ = LL σσ TTTTTTTTTTTTT 2 10 8 ff ss 1 σσ TT = 0.67 10 24 cccc 2 (full spectrum) repetition rate: ff = 3.2 kkkkkk
Thomson Scattering J. J. Thomson Nobel prize 1906 Thomson scattering = elastic scattering of electromagnetic radiation by an electron at rest the electric and magnetic components of the incident wave act on the electron the electron acceleration is mainly due to the electric field the electron will move in the direction of the oscillating electric field the moving electron will radiate electromagnetic dipole radiation the radiation is emitted mostly in a direction perpendicular to the motion of the electron the radiation will be polarized in a direction along the electron motion
Thomson Scattering J. J. Thomson Nobel prize 1906 ddσσ TT θθ ddω = 1 2 rr 0 2 1 + cccccc 2 θθ differential cross section rr 0 = ee 2 4ππεε 0 mm ee cc 2 = 2.818 10 15 mm classical electron radius σσ TT = ddσσ TT θθ ddω ddω = 2ππrr 2 0 2 1 + cccccc2 θθ ddθθ 0 ππ = 8ππ 3 rr 0 2 = 6.65 10 29 mm 2 = 0.665 bb
Scattered photons in collision EE γγ = 2γγ ee 2 1 + ccccccθθ LL 1 + γγ ee θθ γγ 2 + aa0 2 + 4γγ eeee LL mmcc 2 EE LL θ = π θ = 0 ssssssθθ = 1/γγ
Inverse Compton scattering of laser light
Extreme Light Infrastructure Nuclear Physics
Nuclear Resonance Fluorescence Widths of particle-bound states: Γ 10eeee Breit-Wigner absorption resonance curve for isolated resonance: σσ aa EE = ππλλ 2 2JJ + 1 2 Γ 0 Γ EE EE 2 rr + Γ 2 2 ~ Γ 0 Γ Resonance cross section can be very large: σσ 0 200 bb (for Γ 0 = Γ, 5 MeV) Example: 10 mg, A~200 N target = 3 10 19, N γ = 100, event rate = 0.6 [s -1 ]
Nuclear Resonance Fluorescence Count rate estimate 10 4 γ/(s ev) in 100 macro pulses 100 γ/(s ev) per macro pulse example: 10 mg, A ~ 200 target resonance width Γ = 1 ev 2 excitations per macro pulse 0.6 photons per macro pulse in detector pp-count rate 6 Hz 1000 counts per 3 min narrow band width 0.5% 8 HPGe detectors 2 rings at 90 0 and 127 0 ε rel (HPGe) = 100% solid angle ~ 1% photopeak ε pp ~ 3%
Nuclear Resonance Fluorescence narrow bandwidth allows selective excitation and detection of decay channels
Deformation and Scissors Mode Decay to intrinsic excitations