Band structure and wave-number data for band lines. Using an active nitrogen source, the /3 bands of NO included in the region of 2300 to 5300A have been photographed in the second order of a 21-ft. Rowland concave grating. Each complete band consists of two sub-bands with a P and an R branch of the ordinary type and also a very weak Q branch. The latter is relatively more intense in the lower frequency sub-band. Here there are four missing lines in the otherwise continuous P -R series, while there are two in the higher frequency sub-band. The lines of the latter are narrow doublets superficially resembling those of the violet CN bands. The six branches for each of eighteen bands have been measured, and wave-numbers are tabulated for 20 to 30 lines in the P and R branches, and for the few visible members of the Q branches. The bands measured include nine of the strong w'=0 progression (w"=4tol2),threeofw' = l(w"=6, 11, 13), four of w '=2(»"=9, 13, 14, 15), and two of »'=3(»"=8, 16).Isolation and representation of spectral terms. Combinations involving the P and R branches are found to hold, and show the existence of four different sets of rotational terms, two (one for each sub-band) in the initial electronic state and similarly two in the final state. For low values of j the rotational terms in all four cases are representable by F(j) = B(j 2 -a 2 ). From a consideration of the missing lines, the observed transitions are classified as 2 Pi-» 2 Pi, with a' = 2 P2,
An electromagnetic method of separating gas ions of different mass, such as that used by Dempster, has been employed in a study of the ions produced by electron impact in water vapor. The principal ions appearing were (H 2 0) + and (OH) + . Of these the (H 2 0) + ions were more abundant. Unmistakable evidence was obtained that a third type of ion, probably (H 3 0) + , was produced in very small quantities. H + and H2 4 " ions were always very few in number or unobservable. No (OH)~ or any other negative ions were observed.Ionization potentials for (H 2 0) + and (OH) + .-The ionization potential corresponding to (H 2 0) + was 13 + 1.5 volts, being probably in agreement with the ordinarily measured ionization potential. The (OH) + ionization potential was not distinguishably different, but it was difficult to measure this quantity owing to some overlapping of the (H 2 0) + and (OH) + peaks.Relative abundance of the ions as a function of pressure.-A study was made of variation in the relative abundance of the ions as a function of pressure. The (H 2 0) + ion appears to be the primary ion, as it predominates at low pressures, but is of the same order of magnitude as the (OH) + ion at high pressures (0.007 mm).
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