Light-Pressure-Induced Shifts of 2^3S(J=1) = 2^3P(J=0,1,2) Helium Lines   in a Vapor Cell and Implications for the Fine Structure Constant Measurement
  This paper has been temporarily withdrawn by the authors. In the process of 4He 2P fine structure measurement in a vapor cell, highly nonlinear dependences of 2S_1 - 2P_J intervals on helium density are observed and attributed to light pressure. If total angular momentum of the excited state is not greater than that of the ground state, there are large polarization dependences and variations of shifts with helium pressure that exhibit apparent singularities. A pressure-variable cell may be a better system for control of this effect than an atomic beam. A method of avoiding the shifts for the fine structure measurement is suggested. 
T. Zelevinsky