Shifts of the n = 4 hydrogen and 3 3D helium levels induced by TEA CO2 laser radiation P. Pignolet, A. Bouchoule, P. Davy, B. Dubreuil et P. Wackherr J. Physique Lett., 40 17 (1979) 431-434 DOI: 10.1051/jphyslet:019790040017043100