Ion-imaging and dispersed fluorescence spectroscopy are employed for the photodissociation dynamics study of methylamine in the photolysis wavelength range 205–213 nm. The methyl radical product is found to populate a wide range of ro-vibrational states, among which the CH3 fragment generated in the v = 0 state shows a bimodal kinetic energy distribution. The internal energy analysis of the NH2 counterproduct indicates that a lower kinetic energy component, which was observed only with the CH3(v=0) fragment, energetically matches the electronically excited Ã2A1 state. The dispersed fluorescence spectrum, whose band structure is assigned to the Ã2A1 → X̃2B1 transition, provides evidence of the CH3(v=0) + NH2(Ã2A1) pathway. The branching mechanism of the product pathway is discussed in terms of nuclear dynamics in the long-range region, where the conical intersection between the excited- and ground-state potential energy surfaces can play a significant role.

The photodissociation dynamics of nitromethane (CH3NO2), following photoabsorption at 213 nm in the π∗ ← π transition, has been studied using ion-imaging. The state-resolved velocity and angular distributions were measured for the CH3, NO, and O atom fragments. The CH3 velocity distribution consisted of two peaks with different angular distributions; the slow and fast components showed isotropic and anisotropic distributions, respectively. The NO and O fragments also showed slow components with isotropic angular distributions. The results observed consistently indicate that these slow photofragments were possibly produced by the concerted three-body dissociation channel.Graphical abstractHighlights► Photodissociation dynamics of nitromethane (CH3NO2) following the π–π∗ transition. ► State-resolved scattering distributions observed for the CH3, NO, and O fragments. ► The slow and isotropic component appeared in common for the three photofragments.

We have constructed a photoelectron imaging spectrometer with super-resolution image processing and have applied it to the photoionization of nitric oxide and benzene in molecular beams. A field programmable gate array is employed for real-time subpixel centroiding calculations on hardware, providing 64 megapixel resolution (8192 × 8192 pixels). We examined eight different centroiding algorithms based on the center-of-gravity (COG) and Gaussian fitting (Gauss) methods and have found that the two-dimensional COG (2D-COG) and weighted mean of Gaussian center (w-Gauss) methods have the best performance. The excellent performance of the instrument is demonstrated by visualizing a 25 μm diameter pore structure of an MCP, indicating a spatial resolution of 0.03%. The photoelectron image in one-color (1 + 1) resonance-enhanced multiphoton ionization of nitric oxide using a nanosecond laser provided a photoelectron kinetic energy resolution of 0.2%. This resolution is currently restricted by charged-particle optics. The photoelectron energy and angular distributions in the one-color (1 + 1) resonance-enhanced multiphoton ionization of benzene via 61 and 6111 vibronic levels in the S1 state are also presented. The results demonstrate that photoelectron angular anisotropy varies with the photoelectron kinetic energy and the vibronic state of the cation.

•We investigate the photodissociation dynamics of methyl nitrite.•Moderate vibrational excitation and highly rotational excitation of NO are observed.•The rotational state distribution of NO is well represented by a Gaussian function.•The state-resolved scattering distributions of the NO product are measured.•The translational energy release is closely correlated to the NO rotational energy.State-resolved scattering distributions of the NO product in the photodissociation of CH3ONO were measured at 213 nm with resonantly-enhanced multiphoton ionization spectroscopy and ion-imaging. The spectra of the NO product displayed the vibrational population up to the v = 3 state having the rotational state-distribution with a Gaussian-like function. The scattering data of the NO (v = 1) product indicate that the rotational excitation of the NO fragment and the translational energy release are fairly well compensated. This result is explained as being an outcome of the strong repulsion in the CH3ONO bond in the S2 state.