chapter2 inelastic x-ray scattering at high pressure
2016-01-07 06:21:50 2 举报the interaction between photon and phonon
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linear response
no distinct orientational direction
scalar product
The adiabatic approximation
INS
the phonon polarization and the scattering vector should parallel
IXS
derive the actual count rate
probe system interaction
energy of the neutrons is comparable to the phonon energies
scattering of the photon from the electron charge
coupling of the electron spin with the magnetic photon field
the scattering process takes place on a spherical shell in reciprocal space not a point
photon-electron interaction hamiltonian
longitudinal modes
calculated
direction of the momentum transfer is not defined
scattering spectrum contains information on the density of the state of vibrational mode
thomson scattering
non-resonant term
probed
independent
perturbation theory
neglected
no electronic excitations
scattering process is dominated by thomson term and the resonant and spin dependent contributions to the electron-photon interaction can be neglected
fermi golden rule
scattering from phonons in crystalline systems
double differential cross section
the spin orbit interaction in presence of the electromagnetic field
optimal scattering volume
transverse modes
advantage to study high Z material
the can hove representation
the scattered intensity
determined
along the main symmetry crystalline axis two different modes
atomic displacement parallel to the direction of the wave vector
described
factorization of the form factor
momentum transfer excite several longitdinal and transverse phonon modes
not lead to electronic excitations
stomic displacement perpendicular to the direction of the wave vector
a selection rule for detecting phonons
energy and momentum conservation
intrinsic properties of the sample
incident flux
the absorption emission of a photon by the electron system
beam line ID-28 at European SynchrotronRadiation Facility
difference is only due to lattice excitations
INS crossing section is weak to allow for a large penetration dept
valence electrons close to the fermi level is small compared to the core electrons
final form
allows to have the maximum signal
photoelectric absorption
polycrystals
oriented single crystallites
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