Polarizability cannot be calculated for J=0 state

[fischchr]

The polarizability for J = 0 states cannot be calculated due to a divide by zero in the calculation of the prefactor for the vector polarizability

atomphys/atomphys/calc/polarizability.py

Line 227 in d8b20d3

C1 = A * cos(θk) * mJ / J

A J = 0 state does not have a vector polarizability since the Clebsch-Gordan coefficient <J=0, mj; 1, 0| J=0, mj> = 0 appearing in eq. (10) of http://dx.doi.org/10.1140/epjd/e2013-30729-x is zero.
Therefore,

if J == 0:
    C1 = 0
else:
    C1 = A * cos(θk) * mJ / J 

solves the problem.