In mathematics and numerical analysis, the Ricker wavelet ψ = 2 3 σ π 1 / 4 e − t 2 2 σ 2 {\displaystyle \psi ={\frac {2}{{\sqrt {3\sigma }}\pi ^{1/4}}}\lefte^{-{\frac {t^{2}}{2\sigma ^{2}}}}} is the negative normalized second derivative of a Gaussian function, i.e., up to scale and normalization, the second Hermite function. Wikipedia