Noun
quasimomentum (plural quasimomentums or quasimomenta)
crystal momentum
To U-process to occur the decaying phonon to have a wave vector q 1 that is roughly half of the diameter of the Brillouin zone, because otherwise quasimomentum would not be conserved. Source: Internet
Phonon quasimomentum is defined as ℏq and differs from normal momentum because it is only defined within an arbitrary reciprocal lattice vector. Source: Internet