Redus F. Holland

Study of the A → X Transitions in N2+ and CO+

Optical emissions from long‐lived, excited states of CO+ and N2+ in ion beams have been studied. CO or N2 is ionized by electron impact, and the ions are removed from the ion source to the observation region. Spectra of emission from CO+ and N2+ are obtained for wavelengths in the ranges 3200–5200 A and 6000–8700 A, respectively. All of the spectral features can be ascribed to the CO+ comet‐tail and N2+ Meinel emission systems. The electronic transition moments, Re, for these two emission systems are determined and are found to vary rather slowly with wavelength over the wavelength ranges for which we have data. Lifetimes of the v′=1, 2, 4, and 6 vibrational levels of CO+ (A 2π) are found to be 3.49, 2.78, 2.63, and 2.41 μsec, respectively. Lifetimes of the v′=2, 3, 4, and 5 vibrational levels of N2+(A2πu) are found to be 12.28, 10.70, 10.08, and 9.14 μsec, respectively. The dependences of the measured lifetimes on v′ are consistent with the experimental values of Re and with available Franck‐Condon fact...

Excitation of Nitrogen by Electrons: The Lyman–Birge–Hopfield System of N2

The intensity of vacuum ultraviolet emission produced by a beam of electrons in nitrogen has been measured to determine the probability of exciting the Lyman–Birge–Hopfield (LBH) bands of N2. Measurements included spectral scans of the region 1250–2150 A and scans across the electron beam with a photometer sensitive in the range 1230–1800 A. Some 60 spectral features were attributed to LBH bands. Emission in these bands persisted in a glowing region outside the electron beam. At low gas pressure (0.1 μ), relative band intensities are in rough agreement with values calculated by assuming the Franck–Condon principle applies in excitation and emission. At higher pressure, the intensity was increased by secondary processes, and bands with lower υ′ were enhanced relative to other bands. Photometer scans at low pressure yielded a profile of the glow around the beam which was fairly consistent with a profile calculated by assuming a radiative lifetime of 80 μsec for the parent state of the LBH. Based on the calc...

Octahedral fine-structure splittings in ν3 of SF6☆

A report is made of high-resolution spectrum of ..nu../sub 3/ of SF/sub 6/ in which extensive portions of the rotational fine structure in the P and R branches are resolved for the first time. A preliminary analysis was made of this band, and rotational and octahedral splitting quantum numbers to the transitions were assigned. Similar spectra were obtained of the bending fundamental ..nu../sub 4/ at 615 cm/sup -1/.(auth)

Measurement and analysis of the infrared‐active stretching fundamental (ν3) of UF6

High‐resolution spectra of the infrared‐active stretching fundamental ν3 of 238UF6 have been obtained between 620.6 and 633.5 cm−1 using tunable semiconductor diode lasers. Interference from hot bands was suppressed by cooling the UF6 in a supersonic expansion, and useful monomer concentrations were produced with effective temperatures of <100 K. Portions of the band from P(77) to R(66) are illustrated. All transitions from the vibrational ground state have been assigned, and the Q branch has been fully analyzed. A total of 43 line frequencies and 110 frequency differences extending in J to P(77), Q(91), and R(67) has been used to fit seven spectroscopic constants. The ground‐ and excited‐state values of the rotational constant B could be individually determined, and the U–F bond length in the ground vibrational state is r0=1.9962±0.0007 A. The Q branch of 235UF6 has also been analyzed and the 235UF6–238UF6 ν3 isotope shift measured to be 0.603 79±0.000 17 cm−1. The isotope shift and the Coriolis constant...

Emission from Long‐Lived States in Ion Beams. New Band Systems of NO+

A method for investigating radiation from long‐lived, excited states of ions is described. Emission spectra, apparent lifetimes of the excited states, and electron impact cross sections for producing the radiation can be studied. The spectrum of emission from long‐lived states of NO+ in an ion beam has been obtained for wavelengths between 1250 and 2200 A, but no NO+ emissions have been observed in spectral scans of the 2200–3400‐A region. Some of the spectral features are produced by transitions to the X 1Σ+ state of NO+ from the υ′ = 0 and 1 levels of a single electronic state having an internuclear distance 1.157−0.01+0.02 A and an apparent lifetime 135 ± 35 μsec. These two vibrational levels are 7.301 ± 0.006 and 7.511 ± 0.01 eV above the ground state of NO+. The other emissions observed can be characterized by two apparent lifetimes, 10.8 ± 2 and 160 ± 50 μsec, and appear to be produced by transitions to the X 1Σ+ state from several upper states. Tentatively, the energies of the upper states are set ...

Production of Light by Collisions of 2.5–490 eV He+ with N2: NI, N2+ Second Negative, and Unresolved Emissions between 1200 and 3200 Å

The production of light in collisions between He+ and N2 has been studied at primary ion energies, E, between 2.5 and 490 eV. Strong emissions are present between 1200 and 3200 A, and spectra have been obtained for spectral resolutions between 1.5 and 16 A. NI emissions, N2+ second negative (2N) emissions, and strong, unresolved emissions have been found. The total cross section for producing the emission between 1200 and 3200 A is of the order of 10−16 cm2. For E < 40 eV, the cross section for producing the unresolved emissions is greater than the cross section for producing the N2+(2N) emissions. The cross section for production of the NI emissions decreases with decreasing E and vanishes near the threshold energies expected for NI emission produced by He++N2→N++N+He. With decreasing E, total cross sections for the N2+(2N) and unresolved emissions increase. Apparent populations of the vibrational levels of the N2+(2N) parent state depend differently on E; in particular, for E = 490 eV the υ′ = 1 and 2 ...

Visible and near ultraviolet light produced by the radiative decay of long‐lived states in a nitrogen ion beam

Optical emissions from the decay of long‐lived, excited states of 28N2+ and 30N2+ in ion beams have been studied. Spectra are obtained for wavelengths between 3200 and 6000 A. Most (∼ 80%−90%) of the emission is consistent with light emitted in A 2Πu → X 2Σg+ transitions, for A2Πu vibrational levels with ν′ as high as 30. For an electron energy Ee of 63 eV, about 25% of the 28N2+ produced is initially in the A2Πu, ν′ = 2–9 levels; 0.7% is in the ν′ = 10–19 levels; and 0.3% is in the ν′ = 20–30 levels. Energies of N2+ (A 2Πu, v′) states for ν′≤ 30 are found to be close to the energies calculated from formulas that are known to be valid when ν′ ≤ 9. The electronic transition moment Re is found to vary rather slowly for internuclear distances between 0.92 and 1.1 A. Apparent lifetimes of 6–7 μsec have been measured for emission in selected spectral ranges; these apparent lifetimes are consistent with the observed Re and with previously measured lifetimes of the A2Πu vibrational states. The electron energy ...

Infrared absorption spectra of nitrogen oxides in liquid xenon. Isomerization of N2O3 a)

Infrared absorption spectra of nitrogen oxides present when NO and NO2 are dissolved in liquid xenon between 160 and 220 K have been measured. Spectral absorptions of NO, NO2, (NO)2, N2O4, and N2O3 are identified, and integrated absorption cross sections are given for several spectral features. The spectra suggest that symmetric N2O3 and asymmetric N2O3 are in equilibrium in solution and that the energy difference between these two isomers is 1.8±0.2 kcal/mol.

Photolytic separation of D from H in cryogenic solutions of formaldehyde

Isotopic enrichment of hydrogen has been demonstrated in cryogenic solutions. Formaldehyde is photolyzed in liquid xenon and found to decompose with low quantum yield. Identified photolytic products include CO and CO2. Absorption spectra of formaldehyde dissolved in liquid xenon are presented. The ratios (1.28–2) of the photodestruction rates of isotopically labeled formaldehyde are similar to the ratios (1.2–3) of their respective absorption cross sections. The photochemistry is briefly discussed.

Absorptivity of nitric oxide in the fundamental vibrational band

Abstract From observations of the spectral absorbance of mixtures of nitric oxide in nitrogen at room temperature, we derive an integrated absorptivity for the NO fundamental band of 137.3±4.6 cm -2 atm -1 at 0°C. The indicated uncertainty is the estimated maximum error.