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The photodissociation spectrum of SO+2 corresponding to the process SO+2 +hν→SO++O has been measured on a triple quadrupole system for the wavelength ranges: 3000–3400 and 4400–5120 Å. The spectrum in the visible has been assigned to the C̃ 2B1←Ã 2A2 transition and vibrational structure analyzed to yield λ00=4187 Å, the harmonic vibrational frequencies ν̃′1=953 cm−1, ν̃′′2=499 cm−1, ν̃′1=767 cm−1, and ν̃2 =410 cm−1, and the anharmonicity constants X″11 =−6.3 cm−1, X′′12 =−6.1 cm−1, X″22 =−4.2 cm−1, X12 =−6.3 cm−1, and X′22 =−7.4 cm−1. Apparent photodissociation cross sections ranged from ∼1×10−20–1.6×10−19 cm2 in the visible spectrum. In the UV spectrum the highly congested vibrational structure could not be resolved sufficiently for analysis; photodissociation cross sections ranged from ∼2–4×10−19 cm2 with broad bands roughly corresponding to expected progression in ν1 and ν′2 within the C̃ 2B1←X̃ 2A1 electronic transition. The process SO+2 +hν→S++O2 showed an onset near 3108 Å and the corresponding photodissociation spectrum showed sufficient vibrational structure to yield ν̃′′2∼454 cm−1, ν̃′1 ∼955 cm−1, and ν̃2 ∼411 cm−1. This new process, which had σ≤3×10−20 cm2, was proposed to result from the D̃ 2B2←X̃ 2A1 transition. Several new photodissociation cross section measurements on N2O+ have also been made in the vicinities of 3381 and 4880 Å, taking advantage of the high sensitivity (→10−21 cm2) of the triple quadrupole system.

The nature of primary photoprocesses important in the larger cyclic ketones has provoked considerable discussion in recent years, with the formation of biradical intermediates,1 intersystem crossing to a triplet state,2•3 internal conversion to the ground electronic state,4 and predissociation6 all having been invoked to explain diverse results of different workers. We are in the process of a thorough study of the photochemical and photophysical pathways in cyclopropanone which we hope will contribute toward the development of a systematic description of the fundamental factors determining the fates of electronically excited cyclic ketones in general. We wish to present here a preliminary report of our photochemical results for cyclopropanone-the first such report for this compound in the gaseous state.6Upon irradiation of samples of gaseous cyclopropanone, at pressures from ~300 µ to 4 Torr and wavelengths from 2920 to 3650 A, we find ethylene and carbon monoxide to be the only volatile photochemical products. Mass spectrometric analysis of a sample photolyzed to 93% of completion at 3130 A confirmed that these two products are formed in equal amounts within experimental error (~3 %). Other possible products such as acrolein, ketene, and cyclopropanone dimers have been searched for using gas chromatography, ir and uv spectrophotometry, and mass spectrometry without success.We estimate that these compounds could have been detected if they had amounted to as little as 2, 4, and 6%, respectively, of the total volatile products formed in a typical photolysis carried to 10% completion. The quantum yield for disappearance of cyclopropanone, determined by following the decay of absorption in its second uv band at 2057 A (e 763 M_1 cm-1) and using gaseous azomethane as the actinometer,7 was found to be 1.0 within experimental error at all pressures and wavelengths. In contrast, the quantum yield of ethylene formation is(1) R.

The thermal decomposition of methylcyclobutane has been investigated over the temperature range 410-490" and a pressure range 1 x 10-4 to 10 Torr by a mass spectrometric technique. The principal products are ethylene and propylene, but isomerization t o 1-pentene accounts for 0.5-1.8z of the reaction. 'The reaction shows evidence of activation and deactivation by wall collisions below 10 p . A modified form of the Kassel integral is presented which fits the data very well, using EO = 63.1 kcal/mole and an effective 26 oscillational modes. It is found that the collisional deactivation efficiencies for intermolecular and wall collisions are in thc ratios 0.7 and 1.0. as and Walters2 and Pataracchia and Walters8

It has been discovered that a rapid dark reaction occurs on adding platinized Ti02 "photocatalyst" to liquid methanol before and/or during degassing resulting in large amounts of formaldehyde (mostly in the form of methoxymethanol) being present at the start of subsequent photolyses. The kinetics of this reaction has been studied in a magnetically stirred reactor over the temperature range 282-325 K, yielding an activation energy essentially equal to the value for diffusion of 0 2 through CH3OH (1). The rate constants measured at t = 0 are only (2.4 f 0.7) x times theoretical diffusion-limited values, indicating that the rapid reaction only occurs at widely-spaced platinum-coated sites. Turnover numbers as large as 2200 per Ti atom (1.1 x lo7 per active site) were measured after 27 h of reaction. Methyl formate, formic acid, and C02 are observed as secondary reaction products, with some indication of higher hemiformals being formed as well.