Spherical Hankel h (2)
From specialfunctionswiki
The spherical Hankel function $h_{\nu}^{(2)}$ is defined by $$h_{\nu}^{(1)}(z)=j_{\nu}(z)-iy_{\nu}(z),$$ where $j_{\nu}$ is the spherical Bessel function of the first kind and $y_{\nu}$ is the spherical Bessel function of the second kind.