Shifts of hydrogen lines from electron collisions in dense plasmas

The semiclassical impact-parameter method is used to calculate shifts of Lyman and Balmer lines from levels n≤6 caused by electrons in a dense plasma. Comparison with measurements and estimates of shifts due to ion quadrupole interactions indicate that shifts from distant electron-atom collisions are the major cause of observed shifts of Balmer lines. Blue shifts from ion-atom quadrupole interactions are relatively small for low series members.