Ultrafast Deep-Ultraviolet Laser Ionization Mass Spectrometry Applicable To Identify Phenylenediamine Isomers

Abstract

The application of low-fragmentation mass spectrometry to identify chemicals has been recognized to be of particular importance in chemistry, biomedicine, and materials science. Utilizing a customized all-solid-state picosecond-pulsed deep-ultraviolet (DUV) laser, here we present new advances into photoionization mass spectrometry. The DUV laser ionization mass spectrometry (DUV-LIMS) results in very clean spectra pertaining to minimized structure relaxation and fragmentation under the ultrafast ionization process. Typical DUV-LIMS applications are illustrated not only for small organic molecules but also for long-chain unsaturated hydrocarbons and clusters of benzene. The unique advantages of DUV-LIMS enable us to detect and analyze confusing organic compound mixtures, indicating promising applications. DUV-LIMS is also found to be applicable in the identification of phenylenediamine isomers. An in-depth analysis of reaction dynamics is provided showing how hydrogen-atom-transfer (HAT) initiates the distinguishable photodissociation of phenylenediamines under near-resonant excitation. In particular, ortho-phenylenediamine (OPD) finds a remarkable dehydrogenation product with comparable intensity to the molecular ion peak, which is associated with the quantum tunnelling tautomers, providing new subjects for studying intramolecular noncovalent interactions.

Unravelling the Weak Interactions in Binary Clusters of Serotonin and Amino Acid Residues

“…Analyses on the quantum theory of atoms in molecules (AIM) and noncovalent interaction plots based on the independent gradient model (IGM) are carried out using the Multifunctional Wavefunction Analyzer (Multiwfn) software, and visualized by Visual Molecular Dynamics (VMD) package . Also, natural bond orbital (NBO) analysis, molecular electrostatic potential (MEP) analysis, and mutual penetration distance (MPD) analysis are conducted based on the DFT calculations. The generalized Kohn‐Sham energy decomposition analysis (GKS‐EDA) is conducted at the ωB97X−D/6‐311+G(d,p) level of theory by a local version of GAMESS …”

Deep Ultraviolet Laser Radiation Causes Brittle Fracture of Cα‐Cβ Bonds in Neurotransmitters

“…are often correlated with photodissociation depending on the residual energies and the dynamic fragment appearance energy. Figure B sketches the photoionization and photon‐induced dissociation processes involved in the DUV or VUV laser radiation . Under VUV or DUV laser radiation, the molecules undergo single‐photon ionization (SPI) or biphotons ionization (BPI) depending on the ionization energy of the chemical; simultaneously, the transition from molecule ground state to the ionic state (molecular ion) accompanies with likely dissociation/fragmentation depending on the residual energy after ionization, where we introduced the dynamic fragment appearance energy (AE, the necessary energy to allow for detecting the fragment ion).…”

“…In particular, it is noteworthy that the HAT transition‐state energy for histamine is only 0.01 eV (Figure c) on a basis of McLafferty rearrangement, although relatively larger activation energy for the final‐step C α ‐C β dissociation. Comparing with the ultrafast picosecond ionization process by DUV laser, the ns‐pulsed VUV laser excitation could provide longer time for vibrational relaxation and structural rearrangement, thus HAT products could be attained easier …”

“…Note that the ionization energies of the three typical molecules (tyramine, tryptamine and histamine) happen to be slightly larger than the DUV single‐photon energy (7 eV), thus, a two‐photon ionization process with large residual energy accounts for the mass observation. Predominant two‐photon ionization of DUV‐LIMS has been found to be available to identify chemical structures combined with first‐principles density function theory (DFT) calculations . As results, brittle fracture of the C α ‐C β bond is found without hydrogen atom transfer (HAT) or McLafferty rearrangement.…”

A Deep Ultraviolet Mode-locked Laser Based on a Neural Network

“…Almost all materials have a spectral fingerprint in the ultraviolet range [1][2][3][4][5][6][7][8] (especially at 30-200 nm). With increasing attention on deep ultraviolet ellipsometry and more research on the interactions between DUV lasers and matter, the application of deep ultraviolet spectroscopy has spread from various fields of biomedicine [9][10][11][12] to the creation of novel functional materials [13][14][15][16][17] . Also many important transitions, such as the Hydrogen 1S-2S two-photon transition [18][19][20] (243 nm), have DUV and shorter wavelengths.…”