New values for some ${}^{4}{He}$ I $1 s n l$ energy levels, ionization energies, and Lamb shifts

Recent experimental determinations of energy separations within the

1 s n l

term system (

n = 2 - 6

) have been used to reevaluate 35 levels. Most of the levels have estimated errors less than 0.001

{cm}^{- 1}

relative to the

2 {}^{3}P

levels. Addition of accurate theoretical term values (ionization energies) available for several

1 s n l

levels to the corresponding experimental level values gives generally consistent values for the principal ionization energy (

E_{I}

). The theoretical energies are further confirmed by the agreement of the weighted average of seven of these

E_{I}

values with a value obtained by fitting Ritz formulas to three accurately determined

1 s n l

series; the suggested new

E_{I}

is 198 310.7745(40)

{cm}^{- 1}

on an energy scale fixed by the value 171 135.0000

{cm}^{- 1}

for

2 {}^{1}P

. Lamb shifts are derived for the

2

3

4 {}^{3}S_{1}

2 {}^{1}S_{0}

2 {}^{3}P_{1}

, and

2 {}^{1}P_{1}

levels as differences between experimental term values obtained with the new

E_{I}

and corresponding calculated term values not including Lamb shifts. The experimental and calculated values for the

{1 s}^{2} {}^{1}S_{0}

ground level relative to the present

1 s n l

excited-level system are 0.00±0.15 and 0.073±0.009

{cm}^{- 1}

, respectively, so that a ∼20-fold increase in the experimental accuracy would be required to test the calculated ground-level Lamb shift.

This publication has 34 references indexed in Scilit:

New values for someHe4I1snlenergy levels, ionization energies, and Lamb shifts