The pure rotational spectra of the open-shell diatomic molecules PbI and SnI

Pure rotational spectra of the ground electronic states of lead monoiodide and tin monoiodide have been measured using a chirped pulsed Fourier transform microwave spectrometer over the 7-18.5 GHz region for the first time. Each of PbI and SnI has a X (2)Π1/2 ground electronic state and may have a hyperfine structure that aids the determination of the electron electric dipole moment. For each species, pure rotational transitions of a number of different isotopologues and their excited vibrational states have been assigned and fitted. A multi-isotopologue Dunham-type analysis was carried out on both species producing values for Y01, Y02, Y11, and Y21, along with Λ-doubling constants, magnetic hyperfine constants and nuclear quadrupole coupling constants. The Born-Oppenheimer breakdown parameters for Pb have been evaluated and the parameter rationalized in terms of finite nuclear field effects. Analysis of the bond lengths and hyperfine interaction indicates that the bonding in both PbI and SnI is ionic in nature. Equilibrium bond lengths have been evaluated for both species

Ultrafast ionization and fragmentation dynamics of polycyclic atomatic hydro-carbons by XUV radiation

In the interstellar medium polycyclic aromatic hydrocarbon molecules (PAH) are exposed to strong ionizing radation leading to complex organic photochemistry. We investigated these ultrafast fragmentation reac-tions after ionization of the PAHs phenanthrene, fluorene and pyrene at a wavelength of 30.3 nm using pump probe spectroscopy at a free electron laser. We observe double ionization and afterwards hydrogen abstraction and acetylene loss with characteristic time scales for the reaction processes below one hundred femtoseconds

Fragmentation Dynamics of Fluorene Explored Using Ultrafast XUV-Vis Pump-Probe Spectroscopy

We report on the use of extreme ultraviolet (XUV, 30.3 nm) radiation from the Free-electronLASer in Hamburg (FLASH) and visible (Vis, 405 nm) photons from an optical laser toinvestigate the relaxation and fragmentation dynamics of fluorene ions. The ultrashort laserpulses allow to resolve the molecular processes occurring on the femtosecond timescales.Fluorene is a prototypical small polycyclic aromatic hydrocarbon (PAH). Through theirinfrared emission signature, PAHs have been shown to be ubiquitous in the universe, andthey are assumed to play an important role in the chemistry of the interstellar medium. Ourexperiments track the ionization and dissociative ionization products of fluorene throughtime-of-flight mass spectrometry and velocity-map imaging. Multiple processes involved inthe formation of each of the fragment ions are disentangled through analysis of the ionimages. The relaxation lifetimes of the excited fluorene monocation and dication obtainedthrough the fragment formation channels are reported to be in the range of a few tens offemtoseconds to a few picoseconds

Ultrafast ionization and fragmentation dynamics of polycyclic atomatic hydro-carbons by XUV radiation

In the interstellar medium polycyclic aromatic hydrocarbon molecules (PAH) are exposed to strong ionizing radation leading to complex organic photochemistry. We investigated these ultrafast fragmentation reactions after ionization of the PAHs phenanthrene, fluorene and pyrene at a wavelength of 30.3 nm using pump probe spectroscopy at a free electron laser. We observe double ionization and afterwards hydrogen abstraction and acetylene loss with characteristic time scales for the reaction processes below one hundred femtoseconds