Plasma-deposited thin films of polycrystalline diamond were achieved with an arcjet plasma. The jet operated with hydrogen gas with small admixtures of CH4. The diamond films were highly nonuniform, probably due to the very high gradients of the chemical species and temperatures within the arcjet-substrate system. The arcjet apparatus, and optical emission spectra and Langmuir probe diagnostics of the plasma are described. Also presented are results for the surface chemical analysis of the diamond film using surface analysis by laser ionization.

The loss rate O2(a 1Δg) on a variety of surfaces has been investigated. At 300 K, the most rapid deactivants are Cu, Ag, and Co, with Fe, Ni, Pt, and Pd being somewhat less active. Numerous metals exhibit very low activity, including Al, Au, and W. Quite different temperature dependences were observed among the metals, with the activity of Ag decreasing markedly with increasing temperature over the range 220–470 K, that of Ni increasing, and that of Pd showing little change. The loss-rate–temperature profiles of Fe, Co, and Ni are similar, paralleling the behavior observed in a separate study on these three metals for higher-lying electronically excited states O2.

In an attempt to isolate the important parameters governing the production of the 4–5 eV states of O2 generated from O-atom recombination on metallic surfaces, we have investigated the effects of substrate composition and temperature on the intensity of the UV glows that are generated. Of the 22 metals investigated, glow-producing activity is localized in the VIIIb group on the Periodic Table, led by Ni and including Pt, Co, Pd, Fe, and also Au. One parameter that appears to be directly or indirectly linked to this effect is the electronic heat capacity. The six active metals exhibit unique temperature signatures, with Fe, Ni, and Co being distinctly different from Pd, Pt, and Au, measured over the 220–470 K range. The spectra of the UV glows, consisting of the A–X, A′–a, and c–X transitions of O2, differ only in intensity between the metals, not in state or vibrational level distributions. This suggests that the observed spectra are mediated by gas-phase interactions. The data indicate that at high temperatures, surface quenching of the A, A′, and c states is rapid, and that under low-pressure conditions, this effect can be observed even for excited molecules generated in the gas phase. Studies with nickel alloys indicate that the percentage of Ni in a sample is the overriding determinant of the glow intensity, regardless of the other components. Although existing data on energy accommodation coefficients lead to the conclusion that most of the energy in O2 molecules leaving surfaces should be in vibrational modes of the ground state, we have not been able to substantiate this idea.

In the course of studying the reactivity of three organophosphonate compounds with air discharge products, it became desirable to determine the VUV absorption cross sections for these materials [DMMP, (CH3O)2PO(CH3); DEMP, (C2H5O)2PO(CH3); O,S-DEMP, (C2H5O)(C2H5S)PO(CH3)]. Both O2 and O2(a1Δg) are conveniently monitored by VUV absorption, and it was thus necessary to determine the degree of interference that the organophosphonates might cause. To our knowledge, there is no information available on their VUV absorption below 200 nm, whereas significant O2 absorption does not take place above 175 nm.

The 532 nm multiphoton dissociation of NO2 has been investigated, following the work of Matsumi et al. [Laser Chem. 1, 113 (1983)], which demonstrated that highly vibrationally excited O2 (v≤25) is a product. We have shown that O2(v) is generated in a secondary reaction, possibly through the interaction between primary O(1S) and the parent molecule. Competitive quenching experiments with N2 indicate that O(1D) is not involved in O2(v=24) production. Primary NO(v) has been detected by one- and two-photon excitation, with v≤7. Its source is probably 532 nm two-photon dissociation of NO2. The generation of O(1S) requires absorption of four 532 nm photons by NO2.

The absorption spectrum of O2 has been investigated at 930 K in the 1150–1300 Å region. Hot bands associated with ν″ = 1 in the ground state have been seen for each of the strong O2 bands observed over this wavelength range. The 1269 Å band, the identity of which has been somewhat controversial, is shown to be the 0–1 band of the B′3Σu−−X3Σg− transition.

SO was produced from SO2 by pholodissociation with an ArFlaser (193 nm). SO2 chemiluminescence from the SO + O3 reaction was used to monitor the decay of SO and determine rate coefficients for SO reactions with O2 and O3 over the temperature range 230–420 K. The rate expressions are kO2=(2.4+2.6−0.9) x 10−13 exp[(−2370+200−250)/T] and ko3=(4.8+1.6−0.8) × 10−12 exp[(−1170+80−120)/T] cm3 molecule−1 s−1.

Photodissociation of XeF2 with synchrotron light pulses (0.3 ns duration) has been used as the source of the XeF(B, C, and D) excited states. The time-resolved profiles of the intensity of the resulting fluorescence have been recorded and partially analyzed. Most of the measurements were made in the strong XeF2 absorption band between 145 and 175 nm. The absorption cross section was redetermined out to 210 nm, with a maximum value of (5.9±0.5)×10−17 cm2 at 158 nm. By comparison with O(1S) signals from N2O photodissociation, quantum yields for XeF B, C, and D state production were determined. Radiative lifetimes of (14±1) and (100±10) ns were found for the B and C states. Rate coefficients for quenching by XeF2 are reported as are those for converting B to C by collision with Ne, Ar, and N2, along with upper limits for quenching of the C state by these gases.

The O(1S) yield from O3 photodissociation is measured in the 1700–2400 Å region using synchrotron radiation as a light source. An upper limit for the yield is set at 0.1% for the entire photon energy range. This small quantum yield indicates that the contribution of O(1S) to atmospheric OH production is not significant.

Photodissociation of OCS to produce S(1S) has been observed in both liquid argon and liquid nitrogen over the wavelength range 144 to 161 nm. Over this wavelength range, the quantum yields are within a factor of 2 of those previously measured in the gas phase. Spectra of the emissions have been measured. The emissions have radiative lifetimes of (39±2) μsec in liquid argon and (50±3) μsec in liquid nitrogen. Evidence is presented that S(1S) exists mainly as bound molecules in these media and that the lifetimes measured are those for the bound 2 1Σ+−1 1Σ+ transitions. In these media the quenching of the emission by OCS has a rate coefficient of (4±1) ×10−14 cm3 molecule−1 sec−1.

Collision-induced emission from S(1S) has been studied in collisions with He, Ar, N2, H2, Kr, and Xe at 232 and 425°K. The S(1S) was made by OCS photodissociation at 157.7 nm. These results, in conjunction with an earlier study at 296°K, show the importance of bound molecules in the collision-induced emission with Xe—a dissociation energy of ?0.06 eV is estimated for the 2 1Σ+ potential of XeS [the potential arising from Xe+S(1S)]. Evidence for collision-induced emission from bound molecules is found for all except He. In contrast to the other gases, collision-induced emission is a minor process in the removal of S(1S) by hydrogen, accounting for only 0.36% of quenching collisions at 232°K decreasing to 0.12% at 425°K.

The production of S(1S) from OCS, over the wavelength range 142–170 nm, has been investigated at temperatures of 232, 296, and 425°K. Changing the temperature produces no measurable effect on the S(1S) yield in the region of high quantum yield (142–157.7 nm). In the fall off region (157.7–170 nm), raising the temperature increases the quantum yield with the fractional increase growing to longer wavelengths—to a factor of 1.9±0.4 at 170 nm (for a temperature change from 232 to 425°K). Both rotational and vibrational energy may contribute to the effect but, based on considerations of the photodissociation mechanism in this region, vibrational energy (in the bending mode) is thought to play a more important role.

The spectra of collision-induced emission from S(1S) in collisions with He, Ar, N2, H2, Kr, and Xe have been measured. The S(1S) was made by OCS photodissociation with both a xenon resonance lamp (1470 Å) and a CO 4+ lamp (1500–1600 Å). With all gases except xenon, the most obvious effect on the S(1S0→3P1) transition at 4590 Å is the appearance of a neighboring ’’line’’ at 4508 Å corresponding to the S(1S0→3P2) transition. No evidence of the S(1S0→3P0) transition at 4628 Å is seen. Xenon does not produce the 4508 Å emission but results in the appearance of a blue degraded band extending from the 4590 Å line. All of the gases produce a blue degraded band on the S(1S0→1D2) transition at 7727 Å. The implications of these results for the potential curves of XeS are discussed.

The relative O(1S) quantum yield from CO2 photolysis between 1060 Å and 1175 Å has been measured, to sort out the discrepancies between two prior publications on the subject. Whereas the yield is near unity over a considerable portion of the spectral regions, there is an abrupt dip to φO(1S)⩽0.15, centered at 1089 Å. As this wavelength is also the location of a very strong Rydberg transiton in CO2, it appears that the low quantum yield is associated with excitation of the upper level of this transition, the Πu1 state. The O(1D) yield at this wavelength was found to have a minimum value of 0.65±0.1. In conjunction with the lack of any observable fluorescence it is concluded that dissociation on the O(1S)+CO and O(1D)+CO surfaces probably accounts for all the input energy.

Photodissociation of CS2 has been studied over the range 1050–2100 Å. While the quantum yield of S(1S) production is ?0.1 throughout this region, high yields of CS(a 3Π) are produced between 1250 and 1400 Å. Assuming that the quantum yield of CS(a 3Π) production in this region is close to unity, a value of (16±3) msec has been deduced for the radiative lifetime of CS(a 3Π), averaged over the three sublevels. Rate coefficients for quenching CS(a 3Π) by CS2, NO, CO, O2, H2, CO2, N2, Ar, and He have also been measured and compared with the values for CO(a 3Π).