Full configuration-interaction calculations of the angular quantities for helium atom

The angular quantities and < cos theta(12)> for helium atom in both ground and singly-excited states are calculated in the framework of full configuration interaction. The two-electron system wave functions are expanded in terms of the product of Slater-type orbitals. The convergence and accuracy of reported results are examined in detail. From the comparison with previous work, it is shown that the present work establishes the most accurate prediction of the quantity for helium atom up to the present. Radial quantities of < r(<)>, < r(>)>, < r >, and < r(12)> are also reported and compared with previous calculations.