  We establish a relation between the Raman response function in the $B_{1g}$
channel and the electronic contribution to the nematic susceptibility within
the spin-driven approach to electron nematicity of the iron based
superconductors. The spin-driven nematic phase, characterized by the broken
$C_4$ symmetry, but unbroken $O(3$) spin-rotational symmetry, is generated by
the presence of magnetic fluctuations associated with the striped phase. It
occurs as a separate phase between $T_N$ and $T_s$ in systems where the
structural and magnetic phase transitions are separated. Detecting the presence
of nematic degrees of freedom in iron-based superconductors is a difficult
task, since it involves measuring higher order spin correlation functions. We
show that the nematic degrees of freedom manifest themselves in the
experimentally measurable Raman response function. We calculate the Raman
response function in tetragonal phase in the large $N$ limit by considering
Aslamazov-Larkin type of diagrams that contain a series of inserted fermionic
boxes that resemble the nematic coupling constant of the theory. These diagrams
effectively account for collisions between spin fluctuations. By summing an
infinite number of such higher order diagrams, we demonstrate that the
electronic Raman response function shows a clear maximum at the structural
phase transition in the $B_{1g}$ channel. Hence, the Raman response function
can be used to probe nematic degrees of freedom.
