Photoionization of the primary photofragments of chlorine dioxide (OClO) and dichlorine monoxide is (Cl 2 O) reported. The nascent photofragments are formed by UV photolysis, they are subsequently photoionized by time-correlated XUV laser radiation and Ðnally detected by time-of-Ñight mass spectrometry. Primary photolysis of OClO leads to the formation of ClO ] O at j \ 359.5 nm, whereas ClO ] Cl are formed by photolysis of at j \ 250 nm. The XUV photoionization of the photolysis products relies on single Cl 2 O photon ionization. This allows to derive partial photoionization cross sections of the parent cations and their photolysis products from mass spectral intensities by using the absolute photoionization cross sections of the atomic products for calibration. SpeciÐcally, we obtain for OClO at E \ 13.74 eV : Mb and p ClO \ 27 ^5 Mb. Consistent Ðndings are obtained from equivalent experiments on The present p OClO \ 18.5 ^3 C l 2 O. results are compared with previous photoionization work on ClO and OClO to demonstrate the reliability of UV-pump/XUV-probe spectroscopy.

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An experimental device is reported that utilizes time-correlated nanosecond light pulses in combination with photoionization mass spectrometry. A primary light pulse is generated by a tunable dye laser in the ultraviolet regime, which photolyzes neutral gas targets under collision free conditions. Subsequently, a time-correlated extreme ultraviolet-light pulse comes from a laser-produced plasma that is monochromatized in the 10–25 eV regime. The photolysis products are ionized by one-photon absorption, so that the cations are finally detected by time-of-flight mass spectrometry. The performance of this experimental approach is characterized by investigating the primary photolysis products of chlorine dioxide. Finally, possible applications of this approach are briefly discussed.

Photofragmentation of nitryl chloride (ClNO2) is reported in the ultraviolet (UV) (λ = 240 nm and λ = 308 nm) and in the vacuum ultraviolet (VUV) regime (55 nm ≤ λ ≤ 110 nm, corresponding to the photon energy range 11.3 eV ≤ E ≤ 22.5 eV), where pulsed radiation is used to excite the neutral molecule in the gas phase. The neutral photolysis products that are formed upon UV photolysis are subsequently probed by photoionization mass spectrometry by using time-correlated tunable laser-produced plasma VUV radiation. UV-pump/VUV-probe experiments allow us to identify two primary photolysis channels at λ = 308 nm:  (i) Cl + NO2 and (ii) O + ClNO. Primary quantum yields for atomic product formation are deduced from photoionization experiments for both channels:  γ308 nm(Cl) = 0.93 ± 0.10, and γ308 nm(O) = 0.07 ± 0.01. The yield of Cl formation (N(Cl)) is significantly reduced relative to that of O formation (N(O)) at λ = 240 nm, corresponding to a N(Cl)/N(O) ratio of 1.44 ± 0.15. The atomic oxygen is found to be formed in its 3P ground state at both photolysis wavelengths. The present results are compared to earlier work, and atmospheric implications of the present results are briefly discussed. The tunable VUV light source also allows us to perform photoionization mass spectrometry experiments on nitryl chloride without primary photolysis. These experiments yield the first ionization energy of ClNO2 as well as fragmentation thresholds of ClNO2 +.

The single-photon ionization mass spectrometry of primary photofragments of chlorine monoxide (ClO) is reported. The use of laser-produced plasma (LPP) radiation in pump–probe experiments allows us to ionize the laser-generated atomic photoproducts with tunable radiation in the vacuum ultraviolet regime (E = 10–18 eV). Autoionization resonances of the atomic photoproducts are used to establish the quantum states of the photoproducts and to enhance the detection sensitivity. Predissociation and direct dissociation of A (2Π)-excited ClO yields Cl (2 P )+ O (3 P ) as well as Cl (2 P )+ O (1 D ), respectively. The quantum yield of O (1 D ) formation is reported in the threshold regime near the ClO [ A (2Π)] dissociation limit.