The velocity spectrum of metastable H(25) atoms produced by electron bombardment of H2 has been measured by a time-of-night technique. Two distinct groups of metastables have been detected. The slower atoms are interpreted as arising from transitions to attractive states just above the H(lS)-{-H.(2S) dissociation limit. The faster atoms are thought to arise from transitions to doubly excited repulsive states which have not previously been detected.
We have calculated and measured the effective velocity distribution for metastable hydrogen atoms produced in a typical beam apparatus. The distribution is characterized by U n exp(-£/ 2 ), where rc-4 rather than w = 2. We discuss modifications of velocity-dependent corrections to beams measurements of the Lamb shift in the first excited state of atomic hydrogen.
A simple method is proposed for improving the accuracy of WKB eigenvalues by using the WKB eigenfunctions as trial functions in a variational-principle expression for the eigenvalues. The first-order eigenvalues obtained from this estimate are shown to differ from the exact values by terms of order ε6 (where ε is an appropriately defined small parameter that specifies the accuracy of the WKB approximation). For comparison, the fifth-order WKB eigenvalues also differ from the exact values by terms of order ε6. Higher-order variational eigenvalues are also defined, and the third-order estimate is shown to differ from the exact by terms of order ε10. The accuracy of these variational and WKB estimates are illustrated with a numerical example.
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