Photodesorption of CO ices: Rotational and translational energy distributions.

This study investigates the translational and rovibrational energy of vacuum-ultraviolet (VUV) photodesorbed CO molecules from a CO polycrystalline ice (15 K) at ∼8 eV. The electronic excitation was produced by a pulsed VUV laser, and the photodesorption of CO molecules in their ground and first vibrational states was observed using resonance enhanced multiphoton ionization. Time-of-flight and rotationally resolved spectra were measured, and the kinetic and internal energy distribution were obtained.

What does it take to stabilize a naphthalene anion?

We investigate attachment of slow electrons (0-10 eV) to naphthalene (Np) clusters in a crossed beam experiment. Supersonic expansions under different conditions using different buffer gases generate the clusters: in He, Ne, and low pressure Ar, neat (Np)N clusters are formed, while we also observe mixed clusters of naphthalene with rare-gas atoms in co-expansion with Ar above 0.5 bar and with Kr.

On the Wavelength-Dependent Photochemistry of the Atmospheric Molecule CFCOCl.

The wavelength control of photochemistry usually results from ultrafast dynamics following the excitation of different electronic states. Here, we investigate the CFCOCl molecule, exhibiting wavelength-dependent photochemistry both via (i) depositing increasing internal energy into a single state and (ii) populating different electronic states. We reveal the mechanism behind the photon-energy dependence by combining nonadiabatic molecular dynamics techniques with the velocity map imaging experiment.

Pattern recognition as a new strategy in high-resolution spectroscopy: application to methanol OH-stretch overtones.

We further develop a strategy for a line-by-line assignment of complex high-resolution overtone spectra. A search for specific line patterns in the spectrum allows to identify upper rotational states by extending the concept of ground state combination differences (GSCD). Simultaneous use of all GSCDs relating to a given upper state significantly reduces a probability of incorrect assignments.

Energy partitioning and spin-orbit effects in the photodissociation of higher chloroalkanes.

We investigate the photodissociation dynamics of the C-Cl bond in chloroalkanes CH3Cl, n-C3H7Cl, i-C3H7Cl, n-C5H11Cl, combining velocity map imaging (VMI) experiment and direct ab initio dynamical simulations. The Cl fragment kinetic energy distributions (KEDs) from the VMI experiment exhibit a single peak with maximum close to 0.8 eV, irrespective of the alkyl chain length and C-Cl bond position.

Different Dynamics of CH and Cl Fragments from Photodissociation of CHCl in Clusters.

We investigate the photodissociation of CHCl at 193.3 nm using the velocity map imaging technique in (CHCl) clusters in comparison with isolated molecules. Our results for the isolated molecules are in excellent agreement with the previous study of Cl fragments, and we extend it by detecting also the CH(ν = 0) fragments.

Ion and radical chemistry in (HO) clusters.

We investigate the ionization induced chemistry of hydrogen peroxide in (HO) clusters generated after the pickup of individual HO molecules on large free Ar, M[combining macron]≈ 160, nanoparticles in molecular beams. Positive and negative ion mass spectra are recorded after an electron ionization of the clusters at energies 5-70 eV and after a slow electron attachment (below 4 eV), respectively. The spectra demonstrate that (HO) clusters with N≥ 20 are formed on argon nanoparticles.

Long time scale dynamics of vibrationally excited (HBr) clusters.

We investigated the photodissociation dynamics of vibrationally excited HBr molecules and clusters. The species were generated in a molecular beam and excited with an IR laser to a = 1 vibrational state. A subsequent ultraviolet (UV)-pulse with 243 nm radiation photolysed the molecules to yield H-fragments, which were resonantly ionized by the same UV-pulse (2 + 1 REMPI) and detected in a velocity map imaging (VMI) experiment.

Imaging of rotational wave-function in photodissociation of rovibrationally excited HCl molecules.

We demonstrate a visualization of quantum mechanical phenomena with the velocity map imaging (VMI) technique, combining vibrationally mediated photodissociation (VMP) of a simple diatomic HCl with the VMI of its H-photofragments. Free HCl molecules were excited by a pump infrared (IR) laser pulse to particular rotational J levels of the v = 2 vibrational state, and subsequently a probe ultraviolet laser photodissociated the molecule at a fixed wavelength of 243.07 nm where also the H-fragments were ionized.

A simple photoacoustic detector for highly corrosive gases.

In this work, we present a new design of a cantilever-type photoacoustic (PA) detector with high chemical resistance to be used for a broad range of gaseous samples including highly corrosive gasses. A thin mica cantilever used to sense the PA pressure is the only part that comes into direct contact with the sample gas as its deflection is sensed by a probe laser from outside of the gas cell. The design of the detector is simple, compact, and affordable.

OH-stretch overtone of methanol: empirical assignment using a two temperature technique in a supersonic jet.

This paper describes a novel approach for empirical lower state assignments in complex high resolution ro-vibrational overtone spectra of molecules with low rotational constants and complex intramolecular dynamics. Methanol, CH3OH, was chosen as a representative of such molecules - it is an asymmetric top with two non-hydrogen nuclei and hindered internal rotation leading to dense and disordered rotational structure of vibrational overtone bands. We report the first rotationally resolved methanol spectra of the OH-stretch overtone 2ν1 band using sub-Doppler diode laser spectroscopy in a supersonic jet, and describe how the combination of two temperature analysis (TTA) and analysis by ground state combination differences (GSCDs) is used to reliably identify spectral lines that originate from lowest rotational states.

Wavelength resolved UV photodesorption and photochemistry of CO2 ice.

Over the last four years we have illustrated the potential of a novel wavelength-dependent approach in determining molecular processes at work in the photodesorption of interstellar ice analogs. This method, utilizing the unique beam characteristics of the vacuum UV beamline DESIRS at the French synchrotron facility SOLEIL has revealed an efficient indirect desorption mechanism that scales with the electronic excitations in molecular solids. This process, known as DIET--desorption induced by electronic transition--occurs efficiently in ices composed of very volatile species (CO, N2), for which photochemical processes can be neglected.

Spread of multidrug-resistant Streptococcus pneumoniae among hospitalized children in Slovakia.

A multidrug-resistant serotype 14 strain of Streptococcus pneumoniae was isolated from sterile-site specimens and nasopharyngeal secretions from > 200 children in Slovakia between 1985 and 1990. Nasopharyngeal culture surveys were done to determine the extent of spread and means of transmission of this strain. The resistant strain was isolated from cultures of 8 (33.

Multiple antimicrobial resistance of pneumococci in children with otitis media, bacteremia, and meningitis in Slovakia.

Penicillin-resistant pneumococci have been isolated from middle ear fluid, blood, cerebrospinal fluid, and nasopharyngeal secretions of several hundred children in Slovakia since 1985; 116 of these isolates were serotyped and tested for susceptibility to antimicrobial drugs at the Centers for Disease Control and Prevention. To define the prevalence of drug-resistant pneumococci and identify risk factors for infection, laboratory and medical records were reviewed. Nearly all (96%) of the resistant strains tested were serotype 14.