One of the most fascinating predictions of few-body quantum physics is the
Efimov effect, a universal accumulation of an infinite geometric series of
three-body bound states at a two-body scattering resonance. Ever since the
first experimental observation of such an Efimov state, the precise
characterization of their physical properties has continued to challenge
few-body theory. This is demonstrated most strongly by the lithium few-body
puzzle, a remarkable theoretical discrepancy with the observed Efimov spectrum
in 7Li. Here, we resolve this long-standing puzzle, demonstrating
that the discrepancy arises out of the presence of strong non-universal
three-body spin-exchange interactions. This conclusion is obtained from a
thorough numerical solution of the quantum mechanical three-body problem,
including precise interatomic interactions and all spin degrees of freedom for
three alkali-metal atoms. Our results show excellent agreement with the
experimental data regarding both the Efimov spectrum and the absolute rate
constants of three-body recombination, and in addition reveal a general product
propensity for such triatomic reactions in the Paschen-Back regime, stemming
from Wigner's spin conservation rule.Comment: 7+5 pages, 3+2 figure