reporting their measurements on excitation cross sections in helium, also calculated K= 0. 89+ 0. 04. We obtained K= 0. 89 + 0.03 by neglecting the electric field perturbation of the ground state; inclusion of this correction resulted in K = 0. 92 + 0. 03 as reported in Sec. II.Their observed transmission curve for 2'So atoms corresponds to a value of K well below ours; this is due to poorly known velocity distribution and plate separation, neither of which was important to their main work.It was suggested to us that metastable He quenching could serve as a useful method for measuring electric fields in a beam apparatus, since often other considerations of the experiment make it difficult to know the effective plate separation accurately. ' Having measured the transmission of Eq.(6) with K= 0. 926+. 020 gives the field strength uniquely if the velocity distribution is known.We would like to thank B. Schiff for sending us a report of his and Pekeris's work [Schiff and Pekeris (unpublished)].Using their newly calculated oscillator strength between the m'So and n'P& states in Eq. (3), for m = 1 and 2 and n =4 and 5, instead of the corresponding f values of Table I, we arrived at essentially the same values for E. J. Burger and A. Lurio recently measured the oscillator strength between the 1 80 and n P& state, for n=2 and 3. Their results are in excellent agreement with the

No abstract

No abstract