Is there a known orthogonality property of Whittaker functions $W_{kappa,mu}(z)$ with respect to the first index as an integral over the argument? I am particularly interested in the case $mu=0$.
I.e. something of the form

$$ int W_{kappa_1,0}(iz) W_{kappa_2,0}(iz) w(z) d z = delta(kappa_1-kappa_2)$$

for an appropriate integral domain and weight $w(z)$?

What are the best resources for this?