Nuclear Recoils Resulting from the Decay ofBe7

${\mathrm{Be}}^7$ was deposited as a thin film on a Ta foil. The energy spectrum of the ${\mathrm{Li}}^7$ recoils from the reaction ${\mathrm{Be}}^7+e_k\to {\mathrm{Li}}^7+\nu +\mathrm{Q}$ was studied. The observed spectra did not exhibit the monoenergetic character predicted by theory. The maximum energy of the recoils was 56.6±1.0 ev, corresponding to a ${\mathrm{Be}}^7$-${\mathrm{Li}}^7$ mass difference of 860±8 kev. This mass difference, in combination with the best value of the ${\mathrm{Li}}^7\mathrm{}(p,n)\mathrm{}{\mathrm{Be}}^7$ threshold, yields 785±8 kev for $n-H$. Coincidence measurements were made which indicated that monolayer surfaces were probably produced. Auger electrons following the $K$-capture were observed. The variation of the shape of the recoil energy spectrum was studied as a function of the temperature of the backing foil.