Ultrafast dynamics of fluorene initiated by highly intense laser fields.

We present an investigation of the ultrafast dynamics of the polycyclic aromatic hydrocarbon fluorene initiated by an intense femtosecond near-infrared laser pulse (810 nm) and probed by a weak visible pulse (405 nm). Using a multichannel detection scheme (mass spectra, electron and ion velocity-map imaging), we provide a full disentanglement of the complex dynamics of the vibronically excited parent molecule, its excited ionic states, and fragments. We observed various channels resulting from the strong-field ionization regime.

Evolution of the ionisation energy with the stepwise growth of chiral clusters of [4]helicene.

Polycyclic aromatic hydrocarbons (PAHs) are widely established as ubiquitous in the interstellar medium (ISM), but considering their prevalence in harsh vacuum environments, the role of ionisation in the formation of PAH clusters is poorly understood, particularly if a chirality-dependent aggregation route is considered. Here we report on photoelectron spectroscopy experiments on [4]helicene clusters performed with a vacuum ultraviolet synchrotron beamline. Aggregates (up to the heptamer) of [4]helicene, the smallest PAH with helical chirality, were produced and investigated with a combined experimental and theoretical approach using several state-of-the-art quantum-chemical methodologies.

How does the composition of a PAH influence its microsolvation? A rotational spectroscopy study of the phenanthrene-water and phenanthridine-water clusters.

We report on the noncovalent intermolecular interactions established between the polycyclic aromatic hydrocarbons phenanthrene and phenanthridine with water. Such noncovalent interactions involving extended aromatic systems and water molecules are ubiquitous in a variety of chemical and biological systems. Our study provides spectroscopic results on simple model systems to understand the impact that an extended aromatic surface and the presence of a heteroatom have on the nature of the noncovalent interactions established with the solvent.

Far-IR Absorption of Neutral Polycyclic Aromatic Hydrocarbons (PAHs): Light on the Mechanism of IR-UV Ion Dip Spectroscopy.

Gas-phase IR-UV double-resonance laser spectroscopy is an IR absorption technique that bridges the gap between experimental IR spectroscopy and theory. The IR experiments are used to directly evaluate predicted frequencies and potential energy surfaces as well as to probe the structure of isolated molecules. However, a detailed understanding of the underlying mechanisms is, especially in the far-IR regime, still far from complete, even though this is crucial for properly interpreting the recorded IR absorption spectra.

The structural determination and skeletal ring modes of tetrahydropyran.

A high-resolution molecular spectroscopy study was carried out on the cyclic ether tetrahydropyran (THP), one of the smallest molecules composed of a pyranose ring. As this ring structure is closely related to carbohydrates, THP can offer relevant insight into structural variations of this unit. Thus, an extensive probe of THP using three broadband instruments ranging from the microwave to the far-infrared (2-8 GHz, 75-110 GHz and 100-650 cm-1 frequency ranges) was performed to accrue both accurate sets of rotational constants and structural information.

Far-IR and UV spectral signatures of controlled complexation and microhydration of the polycyclic aromatic hydrocarbon acenaphthene.

In this work we report on the experimental and theoretical investigations of the progressional complexation of the polycyclic aromatic hydrocarbon (PAH) acenaphthene with itself and with water. In the interstellar medium, PAH complexes are an important link between molecular gas and solid state configurations of carbon, and in the form of grains they are postulated to serve as chemical catalysts. However, no direct detection of PAHs or their (microhydrated) complexes in interstellar space has been achieved as of yet.

Where's water? The many binding sites of hydantoin.

Prebiotic hydantoin and its complexes with one and two water molecules are investigated using high-resolution broadband rotational spectroscopy in the 2-8 GHz frequency range. The hyperfine structure due to the nuclear quadrupole coupling of the two N atoms is analysed for the monomer and the complexes. This characteristic hyperfine structure will support a definitive assignment from low frequency radioastronomy data.

Chirped-pulse Fourier transform millimeter-wave spectroscopy of ten vibrationally excited states of i-propyl cyanide: exploring the far-infrared region.

We report here further spectroscopic investigation of the astrochemically relevant molecule i-propyl cyanide. We observed and analysed the rotational spectra of the ground state of the molecule and ten vibrationally excited states with energies between 180-500 cm. For this, we used a segmented W-band spectrometer (75-110 GHz) and performed the experiments under room temperature conditions.

Standard free energy of the equilibrium between the trans-monomer and the cyclic-dimer of acetic acid in the gas phase from infrared spectroscopy.

Survey jet-cooled spectra of acetic acid have been recorded in the infrared region (200-4000 cm(-1)) over a wide range of expansion conditions. From the variations of the relative intensities of the signals, vibrational transitions have been assigned unambiguously to the trans-monomer and cyclic-dimer. The IR-active fundamental frequencies have been determined at the instrumental accuracy of 0.

Synchrotron FT-FIR spectroscopy of nitro-derivatives vapors: new spectroscopic signatures of explosive taggants and degradation products.

We report on the first successful rovibrational study of gas phase mononitrotoluene and dinitrotoluene in the TeraHertz/Far-Infrared (THz/FIR) spectral domain. Using the AILES beamline of the synchrotron SOLEIL and a Fourier Transform spectrometer connected to multipass cells, the low-energy vibrational cross-sections of the different isomers of mononitrotoluene have been measured and compared to calculated spectra with the density functional theory including the anharmonic contribution. The active FIR modes of 2,4 and 2,6 dinitrotoluene have been assigned to the vibrational bands measured by Fourier Transform FIR spectroscopy of the gas-phase molecular cloud produced in an evaporating/recondensating system.