Time-reversal of cross-polarization in nuclear magnetic resonance
نویسندگان
چکیده
It is demonstrated that the time evolution of the heteronuclear polarization-transfer process in a dipolar-coupled nuclear spin system can be reversed, leading to the observation of cross-polarization echoes. The cross-polarization echoes are induced by consecutive application of two pulse trains that produce effective Hamiltonians that differ only in sign. Cross-polarization echoes have been recorded for a powder sample of alanine. The time evolution of the spin system is consistent with both unitary quantum dynamics and with spin thermodynamics of two systems approaching a common spin temperature. © 1998 American Institute of Physics. @S0021-9606~98!01923-0#
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