Shining new light on the multifaceted dissociative photoionisation dynamics of CCl₄

Statisticality restored: high internal energy CCl4+ dissociates mostly according to statistical theory, and an intersystem crossing path precludes fluorescence.</p

Advances in threshold photoelectron spectroscopy (TPES) and threshold photoelectron photoion coincidence (TPEPICO)

The history and evolution of molecular threshold photoelectron spectroscopy and threshold photoelectron photoion coincidence spectroscopy (TPEPICO) over the last fifty years are reviewed.</p

Characterisation of a new VUV beamline at the Daresbury SRS using a dispersed fluorescence apparatus incorporating CCD detection

The design and performance of a new normal incidence monochromator at the Daresbury Synchrotron Radiation Source, optimised for experiments requiring high flux of vacuum-UV radiation, are described. The re-developed beamline 3.1, based on the Wadsworth design of monochromator, is the source of tunable vacuum-UV photons in the range 4 – 31 eV, providing over two orders of magnitude more flux than the vacuum-UV, Seya monochromator in its previous manifestation. The undispersed and dispersed fluorescence spectra resulting from photoexcitation of N$_2$, CO$_2$, CF$_4$ and C$_6$F$_6$ are presented. Emitting species observed were N$_2^+$ B$^2\Sigma_u^+$ - X$^2\Sigma_g^+$, CO$_2^+$ A$^2\Pi_u$ - X$^2\Pi_g$ and B$^2\Sigma_u^+$ - X$^2\Pi_g$, CF$_4$$^+$ C$^2$T$_2$ - X$^2$T$_1$ and C$^2$T$_2$ - A$^2$T$_2$, CF$_3$* $^2$A$^’_2$ - $^2$A$^”_2$, and C$_6$F$_6^+$ B$^2$A$_{2u}$ - X$^2$E$_{1g}$. A CCD multi-channel detector has significantly reduced the time period needed to record dispersed fluorescence spectra with a comparable signal-to-noise ratio

A selected ion flow tube study of the reactions of gas-phase cations with PSCl3

A selected ion flow tube was used to investigate the positive ion chemistry of thiophosphoryl chloride, PSCl$_3$. Rate coefficients and ion product branching ratios have been determined at room temperature for reactions with nineteen cations ; H$_3$O$^+$, CF$_3^+$, CF$^+$, NO$^+$, NO$_2^+$, SF$_2^+$, SF$^+$, CF$_2^+$, O$_2^+$, H$_2$O$^+$, N$_2$O$^+$, O$^+$, CO$_2^+$, CO$^+$, N$^+$, N$_2^+$, Ar$^+$, F$^+$ and Ne$^+$ (in order of increasing recombination energy). Complementary data described in the previous paper have been obtained for this molecule via the observation of threshold photoelectron photoion coincidences. For ions whose recombination energies are in the range 10-22 eV, comparisons are made between the product ion branching rations of PSCl$_3$ from photoionisation and from ion-molecule reactions. In most instances, the data from the two experiments are well correlated, suggesting that long-range charge transfer is the dominant mechanism for these ion-molecule reactions ; the agreement is particularly good for the atomic ions Ar$^+$, F$^+$ and Ne$^+$. Some reactions (e.g. O$_2^+$ + PSCl$_3$), however, exhibit significant differences; short-range charge transfer must then be occurring following the formation of an ion-molecule complex. For ions whose recombination energies are less than 10 eV (i.e. H$_3$O$^+$, CF$_3^+$, CF$^+$ and NO$^+$), reactions can only occur via a chemical process in which bonds are broken and formed, because the recombination energy of the cation is less than the ionisation energy of PSCl$_3$

The kinetics and product state distributions from gas-phase reactions of small atomic and molecular cations with C₂H₄, C₂H₃F, 1,1-C₂H₂F₂, C₂HF₃ and C₂F₄

Reactions between atomic and small molecular ions with a series of fluorinated ethenes are studied in a selected ion flow tube. Kinetics and product state distributions are measured. The latter are compared with those from photoionisation.</p