Vacuum Ultraviolet Emission Spectra Research Articles

Absorption and emission spectra of rare-gases in vacuum ultraviolet region

The vacuum ultraviolet absorption and emission spectra of rare-gas van der Waals molecules were observed. A large broadening of at least 240Å of Xe first resonance absorption line was obtained at cell pressure 4 atm. Strong continuous emission of heavier rare gases at 1300 – 3000Å was obtained using self-triggered condensed discharge in a π-shaped quartz discharge tube.

Vacuum ultraviolet spark emission spectra of fluorine and some polyatomic fluorides in noble gases

Spark emission spectra in the vacuum ultraviolet are reported for several polyatomic fluorides in He + Ar mixtures, and for pure fluorine. These results are discussed in terms of the potential of a given fluorine compound for ArF formation. The 158 nm emission in fluorine is tentatively assigned to the 3Π g → 3Π u.

Observation of theH−shape resonance in the hydrogen-arc emission spectrum

Theoretical calculations by Macek and others have shown that the H/sup -/ photoabsorption cross section should be affected by a narrow shape resonance at 1129.5 A. This resonance is expected to cause a noticeable 1.5-A-wide structure in the usual vacuum-ultraviolet emission spectrum of a thermal hydrogen plasma, composed of Lyman line wings, H and H/sup -/ continua, and molecular-H/sub 2/ emission lines. The present paper describes the very thorough investigation of a steady-state local-thermodynamic-equilibrium hydrogen-arc plasma in this spectral region. The arc is operated at atmospheric pressure and its axis temperature ranges from 11 300 to 13 200 K. In contrast to some earlier similar experiments, there is a clear indication of the resonance at exactly the predicted wavelength. The recorded spectra demonstrate that Macek's theory certainly overestimates the strength of the resonance. The reduced oscillator strength of Broad and Reinhardt's more recent calculations can be confirmed, but with half the peak height and twice the width predicted by this theory. This is considered to be an indication for pressure broadening of the resonance in the plasma.

Reexamination of the vacuum ultraviolet emission spectrum of CO in the 950–1200 Å region

New spectrograms of CO below 1200 Å reveal that emission bands terminating on the high energy E 0 1 Σ + and 1Π states plus most of the previously reported unidentified emission bands of CO actually originate from molecular nitrogen. Four new emission band systems in CO, tentatively identified as V 1Π- X 1Σ +, W 1Π- X 1Σ +, Y 1Σ +- X 1Σ +, and Z 1Σ +- X 1Σ +, have been observed. The corresponding T v0 ′s are 98917, 102804, 99963, and 105724 cm −1, respectively.

Emission spectra of solid rare-gas alloys

In this paper we present the results of an experimental study of the α-excited vacuum ultraviolet emission spectra of xenon-argon, xenon-krypton, krypton-argon, xenon-neon, krypton-neon, and argon-neon solid alloys in the temperature range 6–40°K. Three mechanisms for electronic energy transfer to single impurity states and to impurity pairs were considered: (1) energy transfer from vibrationally relaxed homonuclear diatomic molecule of the host to Xe/Ar and to Xe/Kr impurity states; (2) energy transfer from the host vibrationally excited homonuclear diatomic molecule to Kr/Ar impurity states; and (3) energy transfer via impurity ionization or the formation of metastable states in neon alloys. The single impurity emission bands originating from the lowest Wannier states exhibit large red Stokes shifts reletive to the corresponding absorption bands, being close to the corresponding gas-phase transitions, and thus manifest the effect of medium relaxation around single impurity states. A similar effect is exhibited for diatomic molecules in pure solids and for excited impurity pairs. Qualitative information has been obtained regarding efficient nonradiative relaxation processes between high Wannier impurity states. The emitting single impurity state involves in most cases the lowest lying, optically allowed, excited state. We have observed multiple trapping sites for the single impurity and for the impurity pairs in solid Ar and Kr but not in Ne. The population of these trapping sites is determined by the deposition temperature. Finally, spectroscopic evidence is obtained for the existence of heteronuclear rare-gas XeKr* and ArKr* diatomic molecules.

Absorption spectrum in the vacuum ultraviolet and visible emission spectrum of the NO molecule. The 4d complex

The structure of the 4d Rydberg term complex of the nitric oxide molecule has been studied by rotational analyses of the following bands photographed with spectrographs of high resolving power: (i) the weak band 4d–X2Π observed at 1470 Å in the absorption spectrum, (ii) the group 4d–3p of Rydberg–Rydberg bands observed as 4d–C2Π (6400 Å) and 4d–D2Σ+ (6800 Å) bands in the emission spectrum of a discharge. A type of l uncoupling of the Rydberg electron of the molecule is found very similar to the case already known for the 3d complex of NO. Constants characterizing the d complexes are calculated, and a comparison of the 3d and 4d complex is made.

Inner-shell transitions in Ca XII, XIII, XIV and in isoelectronic ions of K, Sc and Ti in laser-produced plasmas

Plasmas generated by focusing Q-spoiled ruby lasers onto solid targets are used as spectroscopic sources for the study of far vacuum ultra-violet emission spectra of ions of astrophysical interest. New, inner-shell transitions of fluorine-, oxygen- and nitrogen-like ions are classified in S X, K XI, XII, XIII, Ca XII, XIII, XIV, Sc XIII and Ti XIV Other new classifications in Cl XII to XIV are also listed

Vacuum ultraviolet light emission from low-pressure hydrocarbon-oxygen flames

The complete vacuum ultraviolet emission spectrum of hydrocarbon-oxygen flames has been measured by working at low pressure to reduce self-absorption and collisional de-excitation. The spectrum is emitted by flames of C 2 H 2 , C 2 H 4 , C 3 H 8 , and CH 4 with approximately the same intensity distribution, but with intensity diminishing in the order given. All the bands correlate with known bands of the CO fourth positive system, and transitions arising from the first seven vibrational levels of the upper state with excitation energies of 185 to 213 kcal/mole have been observed. Two series of quantitative measurements of the emission spectrum have been made for comparison with measurements of chemi-ionization by a Langmuir probe and total collection, respectively. The chemiluminescence arising from CH, OH, C 2 , and possibly CHO as well as the (CO) (O) continuum have also been measured. No evidence of a chemical mechanism linking any of the measured quantities could be found.

Vacuum ultraviolet emission spectra and instrumentation

Vacuum ultraviolet emission spectra and instrumentation