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A new instrument has been constructed for studying the dynamics of photochemical reactions at or near the surface of a liquid. In this apparatus, a liquid microjet is used to deliver a fresh and continuously flowing liquid surface into a high vacuum chamber. This system has been coupled with a laser pump-probe to produce and detect radicals. By using laser-induced fluorescence (LIF) spectroscopy, both the velocity distribution and the population of internal quantum states in the ejected molecules can be determined. Designing and building the apparatus required considerable attention with several significant adjustments being implemented to allow its operation. For instance, a series of traps were required to attain a vacuum in the low 10-5 mbar range. Using Fraunhofer diffraction the stability of the microjet has been demonstrated and the diameter has been confirmed to be 20 µm. To test the pump-probe procedure, a continuous microjet of a toluene/ethanol mixture has been subjected to laser photo-ejection using nanosecond pulses of 266 nm laser light. The time-of-flight distribution of toluene molecules ejected into the gas phase has been measured using time-resolved LIF spectroscopy. The velocity measurement indicated that the laser photejection process generated two groups of ejected molecules: (i) a collection of hyperthermal toluene molecules, which are assumed to be derived from molecules originally at or near the liquid surface and (ii) a group of slower, hotter molecules that most likely emanate from the liquid interior. Concise studies of the other liquid system namely aniline, benzene and acetyl acetone has also been made and are discussed in this thesis.

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No description available.

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No description available.

A series of cyclometallated platinum and palladium(lI) complexes based on the N'C'N coordinating terdentate ligand 1,3-di(2-pyridyl)benzene, HL1, have shown that cyclometalation at C2 of the central ring affords many advantages to square-planar d8-metal complexes. The cyclometalating bond is notably shorter than that observed in many related cyclometallated complexes, e.g. 6phenyl- 2,2'-bipyridine platinum/palladium(lI) chloride and 2-phenylpyridine derivatives. The luminescent properties of the complexes reported herein have been investigated. All complexes are intensely luminescent, in their own right, with quantum yields of luminescence significantly higher than those reported for :related complexes. In the solid-state and at high concentrations, intermolecular interactions create new emissive species, such as self-quenching accompanied 'by excimeric emission observed in solution, Aem =: 700 nm, and multi-centred excited-states in solid samples, Aem =610-700 nm. Modification of both N'C'N and ancillary ligands is shown to manipulate the electronic properties of the d8 _ . metal complexes. Excited-state emission energies have been tuned from 469 nm (blue), L26ptCI, to 588 nm (red), L16ptCI, in the platinum(lI) complexes, and from 466 nm (blue), L1pdCI, to 530 nm (orange), L16pdCI, in the palladium comp!exes. Incorporation of steric incumberance into the ligands can attenuate the excimer emission compared to L1PtCI. Electron-rich pendant ligands encourage the accessibility of charge-transfer excited-states, which adds to the diversity of the photophysical properties, but when coupled with functional groups can give rise to potential in sensory applications. The high quantum yields and special oxygen sensitivity of the platinum complexes have allowed their incorporation into optoelectronic devices. The palladium complexes are of particular interest owing to the limited attention previously paid to palladium complexes as emissive species, particularly, excimeric behaviour is even rarer. Additionally, the electronic tuning which is manifested in the luminescent properties of these complexes has allowed studies into catalytic behaviour of these complexes, revealing some surprising results relating activity to structure.

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No description available.

Ketene has been photolysed both alone and in the presence of inert gases at 3660 and 3130 A/O, at various temperatures. The mechanism for the photolysis at shorter wavelengths, around 2700 A/O, is fairly straightforward because each ketene molecule that absorbs a quantum decomposes and the carbon monoxide quantum yield, equal to two, is independent of temperature and pressure. At 3130 A/O and 3660 A/O, however, deactivation processes play an important part in the photolysis and the mechanisms are more complicated at these wavelengths. At 3660 A/O collisional deactivation has been found to be one-step process, but at 3130 A/O this deactivation process becomes two-step, in certain circumstances. Mechanisms are proposed for ketene photolysis at both these wavelengths. A simpler mechanism used by previous workers is shown to be invalid by its failure to reconcile the experimentally determined rate constants for decomposition, assuming the mechanism, with those calculated from unimolecular reaction theory. The new mechanisms proposed include intersystem crossing whereby excited singlet state molecules cross over to the triplet manifold. Decomposition of both excited singlet state and triplet state ketene molecules occurs, resulting in the production of both singlet and triplet methylene. These two methylenes react differently with hydrocarbons. Recent determinations, with ketene-olefin mixtures, of the proportions of singlet and triplet methylene formed are reviewed.