A direct comparison of the scattering of phonons and rotons from rotons in superfluid 4He

Liquid : an ordinary and exotic liquid

“…The value of the roton group velocity, chosen to match the hf phonon group velocity, means that the high values of σ RR near the resonance are avoided. The ratio of the scattering rates measured by neutrons agree with those from the QE measurements which is pleasing for such diverse techniques [31].…”

Evidence of scattering of bulk elementary excitations in isotopically pure liquid helium-II at low temperatures

“…Some experimental records presented here were taken from [28]. Forbes and Wyatt [29,30] give the first evidence on the scattering of BEEs. Their work [29] uses the technique crossed ballistic BEE beams to investigate the BEE scattering under the right angle, for which some details of employments of the new method were published earlier in [30].…”

“…Forbes and Wyatt [29,30] give the first evidence on the scattering of BEEs. Their work [29] uses the technique crossed ballistic BEE beams to investigate the BEE scattering under the right angle, for which some details of employments of the new method were published earlier in [30]. Note that Wyatt et al's explanation [14][15][16][17][18][19][20] of their experimental results forbids any propagation for the first non-dispersive Zakharenko wave with energy $7 K in the BEE phonon branch owing to the phonon backflow effect measured by W.G.…”