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An analysis of the second spark spectrum of copper is given. The identified levels include all those due to 3d⁹, 3d⁸4s, 3d⁸4p except the ²S and ²P based on 3d⁸¹S. The six levels 3d⁸(³F)5s⁴F, ²F have been found and allow the calculation of an I. P. of 37.08 volts. A number of levels of 3d⁸4d are present also, but 3d⁷4s², which should be lower, has not been found.
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Shenstone et al. (1951) studied this question.
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