In general, we find that the induced dipole spectra exhibit more noise, making smaller peaks such as the C-H stretches around ≈ 3150 cm -1 (area highlighted in blue) hardly visible. Our tests revealed that the induced dipole moments are highly sensitive to the strength of the applied electric field. Even a decrease by ≈ 0.0045 a.u. in the electric field intensity E can introduce so much noise that no peaks are visible at all. Using forward instead of central finite differences might be another, but probably less important, factor contributing to the noise in the spectra. We note that a central-finite-difference approach would double the number of induced-field calculations.