The nuclear reaction can be represented as

${ }_3\mathrm{L}{\mathrm{i}}^7 + { }_1{\mathrm{H}}^1 \to { }_4\mathrm{B}{\mathrm{e}}^8 + { }_z{X}^A$

Applying conservation of atomic number (charge)

$3+1=4+Z \Rightarrow Z=0$

Applying conservation of atomic mass

$7+1=8+A \Rightarrow A=0$

Thus, the emitted particles are $\gamma$-photons $\left({ }_0{X}^0\right).$