Ionization energies and ionization-induced structural changes in 2-phenylethylamine and its monohydrate.

We report the resonance-enhanced two-photon ionization combined with various detection approaches and quantum chemical calculations of biologically relevant neurotransmitter prototypes, the most stable conformer of 2-phenylethylamine (PEA), and its monohydrate, PEA-HO, to reveal the possible interactions between the phenyl ring and amino group in the neutral and ionic species. Extracting the ionization energies (IEs) and appearance energy was achieved by measuring the photoionization and photodissociation efficiency curves of the PEA parent and photofragment ions, together with velocity and kinetic energy-broadened spatial map images of photoelectrons. We obtained coinciding upper bounds for the IEs for PEA and PEA-HO of 8.

Kinetic Energy-Broadened Spatial Map Imaging for Recovering Dynamical Information.

The highly successful velocity map imaging (VMI) technique plays a central role in revealing light-matter interactions. Here we demonstrate the related but distinct kinetic energy-broadened spatial map imaging (KESMI) option for recovering KE and angular recoil information on photophysical processes using a VMI system operating in different out-of-focus modes. The characteristic single or double stripes and related steps in the vertical intensity profiles of KESMIs of photoelectrons (PEs) from Ar ionization allow breakthrough developments of a potent global model that enables an understanding and analysis of these patterns.

Maximal kinetic energy and angular distribution analysis of spatial map imaging: Application to photoelectrons from a single quantum state of HO.

Dynamical or spatial properties of charged species can be obtained using electrostatic lenses by velocity map imaging (VMI) or spatial map imaging (SMI), respectively. Here, we report an approach for extracting dynamical and spatial information from patterns in SMI images that map the initial coordinates, velocity vectors, and angular distributions of charged particles onto the detector, using the same apparatus as in VMI. Deciphering these patterns required analysis and modeling, involving both their predictions from convolved spatial and velocity distributions and fitting observed images to kinetic energies (KEs) and anisotropy parameters (βs).

A new imaging-based method for alignment of multiple laser beams.

A new method for multiple laser beams alignment, useful in a wide range of spectroscopies, is proposed and demonstrated. The method, based on the coupling of spatial map imaging (SMI) with velocity map imaging (VMI), aided beams visualization, through interrogation of the ionization signal of different species in a time-of-flight mass spectrometer. This approach is very effective for alignment and for evaluating the spatial overlap of laser beams with a molecular beam.

Control of Nonadiabatic Passage through a Conical Intersection by a Dynamic Resonance.

Nonadiabatic processes, dominated by dynamic passage of reactive fluxes through conical intersections (CIs), are considered to be appealing means for manipulating reaction paths, particularly via initial vibrational preparation. Nevertheless, obtaining direct experimental evidence of whether specific-mode excitation affects the passage at the CI is challenging, requiring well-resolved time- or frequency-domain experiments. Here promotion of methylamine-d2 (CH3ND2) molecules to spectral-resolved rovibronic states on the excited S1 potential energy surface, coupled to sensitive D photofragment probing, allowed us to follow the N-D bond fission dynamics.