Appearance of negative spin temperature in the presence of a nonresonant acoustic stimulus
Golenishchev-Kutuzov V. A. , Migachev S.A.
An inversion of the nuclear-spin system of Al was observed in a ruby in the presence of steady-state, nonresonant, acoustic saturation at frequencies of 5-70 MHz. It is shown that the interaction of ultrasound with the nuclear-spin system occurs via the nonresonance (relaxation) absorption of ultrasonic-wave energy by the spin system of Cr3+ ions.