Zero Time Resolution Nuclear Magnetic Resonance Transient in Solids

A method is described for the experimental determination of the complete Bloch decay signal after a pulse for broad line nuclear magnetic resonances, as in solids. This method removes the necessity for constructing transient equipment of very short time resolution which would be extremely difficult. By means of apparatus with a time resolution of 3 μsec effectively zero time resolution has been attained. The method is tested by comparing the Fourier transform of the steady state absorption line with the Bloch decay. Agreement to 3% is obtained for many materials having lines up to 15 gauss broad. A theoretical analysis is given which supports the experimental results and which gives an explicit expression for the `echo Bloch decay' up to and including terms of fourth power in the time. Explicit expressions are given for static dipolar interaction for identical spins. It is shown that the second and fourth moments of the absorption lines can be obtained from the echo Bloch decay with an accuracy comparable with that from conventional steady-state methods and these are obtained very rapidly and with little labour.