# Coulombic operator

1. Jun 14, 2007

### greisen

Hi,

I am trying to understand this equation where the coulombic operator is given by

J = \int d\tau \phi(2) \frac{1}{r_{12}}\phi(2)

so I integrate over \tau but what is tau and the number I get from the equation is the energy I pressume?
Any hints or help appreciated.

2. Jun 14, 2007

### Meir Achuz

$$d\tau$$ just represents the differential volume element.
In spherical coordinates, it is $$r^2 dr d\Omega$$.

3. Jun 14, 2007

### greisen

what is that more exactly? I know from spherical geometry that the volume is calculate
dV = \rho^2 sin \phi d\phi d\rho d\theta

If I integrate over two wave functions representing two electrons how to interpreted it?