Band Spectra in the Extreme Ultra-Violet Excited by Active Nitrogen

To determine the amount of energy available in active nitrogen for the excitation of spectra, a vacuum grating spectrograph was used to observe spectra between 2500 and 1000A excited in certain gases in the afterglow. The gases were mixed with glowing nitrogen obtained by flowing nitrogen through a discharge tube containing an oscillatory discharge. H₂, O₂, N₂, CO and NO were studied, of which only CO and NO showed bands in the region mentioned.NO bands excited by active nitrogen.---In addition to the β and γ bands of NO characteristic of the afterglow, a progression was found belonging to another system with the same final levels, i.e., levels associated with the normal electronic state of the molecule. The initial level, identified from published absorption data as an electronic state with zero vibration, is designated as level C, and the new system, as the δ band system of NO. The 0-0 δ-band is at 1915.7A, corresponding to 6.44 volts.CO bands excited by active nitrogen.---A few bands of the fourth positive group of CO were obtained in the afterglow, corresponding to the excitation of vibration states n^'=1 to 6 of electronic level A. The total energy of these levels is from 8.2 to 9.0 volts.Mechanism of excitation by active nitrogen.---The results are discussed in the light of a possible mechanism of excitation proposed by Birge. It is assumed that atoms of nitrogen can combine to form an excited diatomic molecule if the encounter is such that the energy of formation and the relative kinetic energy of the atoms go over into electronic, vibrational, and rotational energy of the molecule. Such encounters will be rare, because both energy and momentum must be conserved in the recombination; therefore the active modification will have a relatively long life. On formation, the molecules have 11.4±{}0.3 volts of energy; part of this is lost immediately by radiation of the α group bands, leaving from 9 to 10 volts in a configuration which is strongly metastable with respect to the normal electronic state. This metastable molecule is considered responsible for the excitation of spectra in the afterglow.