Excitation of the zinc spectrum by collisions of the second kind with excited mercury atoms.—A sealed quartz tube containing zinc vapor at 16.0 mm and mercury vapor at 0.28 mm was illuminated by light of various wave-lengths from the hot and cold quartz mercury arcs and the aluminum spark. The resulting fluorescent radiation, observed with a short focus quartz spectrograph, contained several zinc lines which required more than 4.9 volts for their excitation. To account for these lines it is necessary to assume that mercury atoms in the $2{}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ and $2{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ or $3{}_{}{}^3{}_{}{}^{}D$ states are effective in impacts of the second kind. $2{}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ mercury atoms (energy 6.67 volts) were found to excite the first triplet of the sharp series of zinc requiring 6.62 volts but not the resonance line 3075 which requires 4.01 volts. This indicates that a collision between an excited mercury atom and a normal zinc atom is more likely to be one of the second kind if the energy of the excited mercury atom only slightly exceeds that needed to excite the zinc atom. A band, probably due to HgZn, formed in the excited state or excited by an impact of the second kind, was also observed in the fluorescent light.

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