Energy levels and spectrum of neutral helium (4He I)

A ta bl e of energy levels ba cd on t he most acc ura te obser vation s now availa ble is give n ro r t he neut ral 'H e a tom . Th e wa vele ngths co n ta ined in a rev ised list of 'He I lin es from 320 A to 21132 A are a lso ba sed on t he best meas ure ments, over ha lf of t hem ha ving bee n ca l c ulit~ed from t he wave number se p a rat i o n ~ of a ppropri ate levels. Severa l previollsly disturbin g features of t he ' H e term scheme a rc obv iated by t he rev ised level valu es . In it dj s c u s~i o n of t he ex peri me ntal res ults for t his spect rum some compariso ns wi t h t heor y a re m a cl e.