[填空题]
Calculate the wavelepn3no mg21p;q ngth of photons needed t e.c7 v 6fe.yvttyph,jyfh-wq8.ba6w(0jcp * o produce NMR transitions in free protons in a 1.000-T8b ypejfhhjav 6t-cf, c w 6e7(wyqvp0.t.* .y field. In what region of the spectrum does it lie? c = $m$