Evidence for the coexistence of two density fluctuation modes in molten Li₃₀Bi₇₀ as probed by neutron scattering

¹  Département Physique des Milieux Denses CNRS-IMPMC, Université Paris 6 F-75015 Paris, France
²  CNR-INFM CRS-Soft, c/o Institut Laue-Langevin - BP 156, F-38042 Grenoble, France
³  Dipartimento di Fisica, Università di Firenze - I-50019 Sesto Fiorentino, Italy
⁴  CNR-INFM CRS-Soft, Roma, Italy
⁵  Institut Laue Langevin - BP 156, F-38042 Grenoble, France
⁶  Dipartimento di Fisica, Università di Perugia - I-06123 Perugia, Italy

Received: 7 November 2006
Accepted: 21 May 2007

Abstract

We report on a novel simultaneous observation of two inelastic doublets in the dynamic structure factor of the liquid alloy Li₃₀Bi₇₀. This result establishes the coexistence of two density fluctuation modes in a liquid binary system with disparate mass components. The measurements of the dynamic structure factor of the alloy have been performed on the hot neutron three-axis spectrometer IN1 of the Institut Laue-Langevin with an unprecedented energy resolution in the small wave vector domain. Analysis of the dynamical parameters characterizing the two excitations reveals the acoustic nature of the low-frequency mode and suggests an optic-like nature for the high-frequency mode. A comparison with recent neutron scattering results on pure liquid Bi suggests that the low-frequency mode in the alloy is closely related to the heavier component dynamics.