An independent test for the cosmological constant.

It is shown that the emission from high-redshift extragalactic objects, scattered by the intergalactic electron gas at angular distance theta, has, in comparison to directly observed light from the same quasars or galaxies, a redshift excess of Delta z greater than 0, which is sensitive only to the cosmological constant in the range absolute value of lambda = absolute value Omega0/2 - q0 not greater than 1, or absolute value of Lambda/c-squared not greater than 2 x 10 to the -56th (H0/75)/sq cm. The same holds for another version of the Delta z/theta test based on measurements of angular radii of L-alpha-voids around quasars with line-of-sight extensions Delta z.