Ultraviolet photodissociation dynamics of PCl at 235 nm: three-dimensional ion imaging and theoretical analysis.

The photodissociation dynamics of PCl3 at 235 nm has been studied by monitoring ground state Cl(2P3/2) and spin-orbitally excited Cl(2P1/2) atoms by resonance enhanced multiphoton ionization (REMPI). Also, the PCln+ (n = 0, 1, 2) photoions were observed non-resonantly. The speed distributions and speed-dependent anisotropy parameters β for all these particles have been determined by three-dimensional photofragment ion imaging.

Double-arm three-dimensional ion imaging apparatus for the study of ion pair channels in resonance enhanced multiphoton ionization.

We present a novel experimental configuration for the full quantitative characterization of the multichannel resonance enhanced multiphoton ionization (REMPI) of small molecules in cases when the ion-pair dissociation channel is important. For this purpose, a double-arm time-of-flight mass spectrometer with three-dimensional (3D) ion imaging detectors at both arms is constructed. The REMPI of HCl molecules is used to examine the constructed setup.

Simultaneous imaging of both product ions: exploring gateway states for HCl as a benchmark molecule.

Simultaneous imaging of both positive and negative product ions is used to exclusively study photoion pair formation free from interference of competing fragmentation channels. Resonance enhanced multi-photon excitation allows us to interrogate potential energy surfaces for vastly differing molecular geometries. 3D imaging provides complete fragment information.

Experimental and computational study of the gas-phase reaction of O(1D) Atoms with VF5.

The reactions of O((1)D) atoms with VF(5) at room temperature have been studied by time-resolved laser magnetic resonance at the buffer gas (SF(6)) pressure of 6 Torr. The O((1)D) atoms were produced by the photodissociation of ozone using an excimer laser (KrF, 248 nm). By monitoring the kinetics of FO radical formation, the bimolecular rate constant of O((1)D) consumption in collisions with VF(5) has been determined to be k(VF(5)) = (7.

Proton formation dynamics in the REMPI[2+n] process via the F 1Delta2 and f 3Delta2 Rydberg states of HCl investigated by three-dimensional velocity mapping.

HCl in the bulk gas phase at a pressure of 10(-5) mbar has been excited via selected Q-lines of the two-photon transition band systems F (1)Delta(2)<--X (1)Sigma(+)(1,0) [Q(8)], V (1)Sigma(+)<--X (1)Sigma(+)(14,0) [Q(8), Q(7)] and f (3)Delta(2)<--X (1)Sigma(+)(0,0) [Q(2-6)]. Concerning the V<--X excitation, subsequent photon absorption is known to yield HCl(+), H(n=2)+Cl, H(+)+Cl(-) and H+Cl(4s,4p,3d). Vibrationally excited HCl(+) (v(+) > or = 5) can be photodissociated to H(+)+Cl, and excited atoms can be easily photoionized by absorption of a fourth photon, respectively.

Measurement of the differential cross section of the photoinitiated reactive collision of O((1)D)+D(2) using only one molecular beam: A study by three dimensional velocity mapping.

In order to measure the state selective double differential cross section of a reactive collision, the preparation of the reactants with defined initial velocities and quantum states in number densities high enough to achieve an acceptable count rate is most important. At the same time, secondary collisions have to be prevented in order to ensure that the nascent products are not thermalized. Usually, the best way to control the initial conditions is to use crossed molecular beams, but the number density decreases quadratically with the distance from the nozzle orifice which can be a problem, especially if a molecular product with a large number of populated states is to be analyzed state specifically by REMPI spectroscopy.

Excited Cl((2)P(1/2)) atoms: yield from the photodissociation of SOCl(2) and collisional deactivation by NO(2), CCl(3)H, C(2)H(4), C(3)H(6), and SOCl(2).

Rate constants for the collisional deactivation of spin-orbitally excited Cl* ( identical withCl((2)P(1/2))) atoms by some selected gases at T = 298 K have been determined using time-resolved laser magnetic resonance (LMR) techniques. Cl* atoms were produced by photodissociation of SOCl(2) at 248 nm, and the relative quantum yield of Cl* atoms is determined to be 0.52 +/- 0.

Three-dimensional velocity map imaging: setup and resolution improvement compared to three-dimensional ion imaging.

For many years the three-dimensional (3D) ion imaging technique has not benefited from the introduction of ion optics into the field of imaging in molecular dynamics. Thus, a lower resolution of kinetic energy as in comparable techniques making use of inhomogeneous electric fields was inevitable. This was basically due to the fact that a homogeneous electric field was needed in order to obtain the velocity component in the direction of the time of flight spectrometer axis.

Complete characterization of the constrained geometry bimolecular reaction O(1D) + N2O --> NO + NO by three-dimensional velocity map imaging.

The bimolecular reaction O((1)D) + N(2)O --> NO + NO was photoinitiated in the (N(2)O)(2) dimer at a wavelength of 193 nm and was investigated by three-dimensional (3D) velocity map imaging. State selective 3D momentum vector distributions were monitored and analyzed. For the first time, kinetic energy resolution and stereodynamic information about the reaction under constrained geometry conditions is available.

Intermediate state polarization in multiphoton ionization of HCl.

The paper presents the detailed theoretical description of the intermediate state polarization and photofragment angular distribution in resonance enhanced multiphoton ionization (REMPI) of molecules and the experimental investigation of these effects in the E(1)Sigma(+) and V(1)Sigma(+) states of HCl populated by two-photon transitions. It is shown that the intermediate state polarization can be characterized by the universal parameter b which is in general a complex number containing information about the symmetry of the two-photon excitation and possible phase shifts. The photofragment angular distribution produced by one- or multiphoton excitation of the polarized intermediate state is presented as a product of the intermediate state axis spatial distribution and the angular distribution of the photofragments from an unpolarized intermediate state.

Photoionization and photodissociation of HCl(B 1Sigma+, J=0) near 236 and 239 nm using three-dimensional ion imaging.

The electronically excited states HCl(*)(E,upsilon(')=0,J(')=0) and HCl(*)(V,upsilon(')=12,J(')=0) have been prepared by two-photon resonant absorption of ground state HCl via Q(0) transitions at 238.719 and at 236.000 nm, respectively.

Photodissociation dynamics of SOCl2.

New theoretical and experimental results for the ultraviolet photodissociation dynamics of thionyl chloride (SOCl2) are presented and combined with existing data from a variety of sources in order to provide a unified view of the photodissociation dynamics of SOC12. Time-dependent density functional theory on the basis of the hybrid-type B3LYP functional was employed to calculate vertical excitation energies for the SOCl2 parent molecule up to 6.3 eV.