The HeBr2 van der Waals complex has been observed in a free jet expansion. The complex was detected by laser excitation of the bands associated with the Br2(B−X) system. High resolution (0.05 cm−1) spectra have been recorded for the 11-0 to 38-0 bands. The rotational structure has been resolved for several bands and the analysis is found to be consistent with a rigid T-shaped geometry. The distance from the Br2 bond center to the He atom is 3.8 A and 3.7 A for the excited and ground states, respectively. Vibrational predissociation of the He–Br2 bond has been observed via homogeneous broadening of the rotational lines. Predissociation rates, derived from the line shape data, showed a strong dependence on the Br2 vibrational excitation. Rates varied from 1010 s−1 for v′=11, up to 5×1011 s−1 for v′=38. The data can be adequately described by a simple ‘‘energy gap’’ model for the predissociation probability.

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Relative ground state CF and CF2 concentrations have been measured in a 13.56-MHz rf CF4/Ar discharge using both laser-induced fluorescence (LIF) and actinometric techniques to assess the validity of actinometry for CF and CF2 over a limited parameter space of pressure and power. Relative measurements of the CF ( A2Σ − X2Π) system and the CF2 ( A1B1 − X1A1) system were made by LIF. Actinometric values were calculated from relative measures of the plasma-induced emission (PIE) intensity of the CF* ( B2Δ− X2Π) at 202.4 nm, CF2* ( A1B1 − X1A1) at 251.9 nm, and Ar* [4s′(1/2)°−4p′(1/2)] at 750.4 nm. Both LIF and PIE signals were spatially averaged over the bulk of the plasma. Steady-state actinometric and LIF measurements were compared for CF4/5% Ar discharges at pressures in the range of 500 to 1000 mTorr and nominal powers in the range of 20 to 100 W. Dynamic actinometric and LIF measurements of CF were made by modulating the discharge power and monitoring the CF transient at one set of conditions, 500-mTorr pressure and 70-W nominal power. Our results indicate that actinometric measurements of CF and CF2 correlate well with relative CF and CF2 LIF measurements under the studied conditions.

Articles you may be interested inA simple but accurate potential for the naphthalene-argon complex: Applications to collisional energy transfer and matrix isolated IR spectroscopy Visible laser excitation (460-725 nm) of dilute rare gas/12 (2000: 1) matrices resulted in emission from the lzA 3TI ( 1 u ) state. Reanalysis of the A.-X spectra provided revised molecular constants for matrix isolated 1 2 , A state lifetimes of 70 ± 20, 80 ± 20, and 110 ± 30 f.Ls were observed in Ar, Kr, and Xe hosts, respectively. Excitation spectra for the A state closely followed the 12 continuum absorption spectrum, indicating that transfer from the B 3TI(Ou+) and ITI(1u) states was effective in populating Iz(A). At dilution ratios of 600: 1 or lower the I 2 P 1/2 _2 P 3/2 transition was observed in conjunction with the A-X bands. Excitation studies showed that isolated I atoms, trapped during the deposition process, were excited by energy transfer from nearby If molecules. A vibronic progression, similar to the A-X bands, but shifted to longer wavelengths, was noted in concentrated Rg/lz (300: 1) matrices. This system, which was emitted with a lifetime of about 10 ms, most probably originated from perturbed 12 A' 3TI(2 u )' Intermolecular energy transfer was observed in matrices that contained 12 codeposited with 02' Electronic excitation of I z resulted in a long-lived emission from O 2 a I Ll g • Matrices containing high concentrations of iodine also exhibited 02(a) .-1(2p II 2 ) transfer. . R FI G. 1. Approximate potential energy curves for selected low-energy electronic states of 1 2 , 674

Using a continuum model based on dc field data, the discharge physics of Ar and SF6 has been simulated for 13.5-MHz excitation. In Ar, the ionization primarily occurs at the bulk–sheath interfaces and is temporally modulated with its maximum corresponding to the cathodic phase of the rf cycle. In SF6, the ionization is distributed throughout the bulk with a maximum occurring at the bulk–sheath interface and a temporal maximum occurring during the anodic phase. The plasma induced emission (PIE), which correlates with the predicted ionization rate, has been experimentally measured as a function of position and time and agrees well with the model predictions. These results explain the phase shift of the PIE between electronegative and electropositive discharges.