Infrared emission spectra of krypton and argon.

The analysis of the spectra of the noble atmospheric gases, utilizing descrip tive daLa cove ring the photographicall y accessible region, has long indicated the possibili ty of a considerable ex te nsion of most of t hese spectra into the infrared r egion beyond 1.3 microns. Obse r vations of the spectra of krypton a nd a rgo n, in the region be tween 1 and 2 mi crons, have bee n made with a Perkin-Elmer spec trometer, fi tted wi th a flin t-glass prism cut to an anglc of 55 degrees. Tlw sources " 'e re Ce is ler tubes, used in prev ious ly reported work. More than ] 5 new lineR of krypto n have bee n obse rved. P art of these are blends of unresolved pairs or groups. The emission maxima have been determined in favorabl e cases to a precision of two wave numbers, roughly equi valent to onete nth of t he smallest scale division on the wavelength drum. All observed lines have been classifi ed, the mos t inte nse being represented by com binations of the type 2p3d, accordi ng to Paschen's notaLio n. Two new levels from the confi gura tion S2 p5J have bee n found . T he remaining unobse rved combinations of t he type l s2p, occurr ing in this region , arc, with one exception , too weak to be ob e rved. The a rgon infrared spectrum was observed by Paschen. More of i ts pred ic ted combi nat ions a re ill t he photographic r egion than in the case of krypton. A few lines near 1.4 microns ha\'e bee n obse rved,