chapter2 inelastic x-ray scattering at high pressure

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