$${d_2=d_1+ \frac{\lambda}{4(n_0-n_e )} =7,35 \cdot 10^{-4}- \frac{5,46 \cdot 10^{-7}}{4 \times (1,5553-1,5462)}=7,2 \cdot 10^{-4}\, \mathrm{m}}$$