Ethylene glycol dinitrate (EGDN) is a nitrate ester explosive widely used in military ordnance and missile systems. This study investigates the decomposition dynamics of EGDN cation using comprehensive approach that combines femtosecond time-resolved mass spectrometry (FTRMS) experiments with ab initio electronic structure molecular computations. We identify three distinct dissociation time scales for metastable approximately 40-60 fs, 340-450 >2 ps. The observed are rationalized by...

Spectroscopic, thermal, and electrochemical characterization results are presented for the redox active polymer poly(2,2,6,6-tetramethyl-1-piperinidyloxy-4-yl methacrylate) or PTMA, synthesized by group transfer polymerization (GTP), its precursors 4-hydroxy-tetramethylpiperidine-N-oxyl (HO-TEMPO) 4-methacryloyloxy-tetramethylpiperidine-N-oxyl (MO-TEMPO). DSC analysis of PTMA showed that glass transition temperature (T(g)) structure occurs at 155 °C, corroborated dynamic mechanical (DMA),...

0rtho-Nitroaniline (ONA) is a model for the insensitive high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) that shares strong hydrogen bonding character between adjacent nitro and amino groups. This work reports femtosecond time-resolved mass spectrometry (FTRMS) measurements theoretical calculations explain stability of ONA cation compared with related nitroaromatic molecules. Ab initio found lowest-lying electronic excited state cation, D1, lies more than 2 eV above ground state,...

Discrimination of isomers in a mixture is subject ongoing interest biology, pharmacology, and forensics. We demonstrate that femtosecond time-resolved mass spectrometry (FTRMS) effectively quantifies mixtures ortho-, para-, meta-nitrotoluenes, the first two which are common explosive degradation products. The key advantage FTRMS approach to quantification lies ability pump–probe laser control scheme capture distinct fragmentation dynamics each nitrotoluene cation isomer on timescales,...

We report density functional theory computations and photoionization mass spectrometry measurements of aniline its positively charged ions. The geometrical structures properties the neutral singly, doubly, triply are computed using with generalized gradient approximation. At each charge, there multiple isomers closely spaced in total energy. Whereas lowest energy states both cation have same topology C6H5–NH2, dication trication C5NH5–CH2 nitrogen atom meta- para-positions, respectively....

We report new insights into the ultrafast rearrangement and dissociation dynamics of nitromethane cation (NM+) using pump-probe measurements, electronic structure calculations, ab initio molecular simulations. The "roaming" nitro-nitrite (NNR) pathway involving large-amplitude atomic motion, which has been previously described for neutral nitromethane, is demonstrated NM+. Excess energy resulting from initial population electronically excited D2 state NM+ upon strong-field ionization...

We report on pump-probe control schemes to manipulate fragmentation product yields in p-nitrotoluene (PNT) cation. Strong field ionization of PNT prepares the parent cation ground electronic state, with coherent vibrational excitation along two normal modes: C-C-N-O torsional mode at 80 cm-1 and in-plane ring-stretching 650 cm-1. Both wave packets are observed as oscillations fragment ion mass spectrum upon optical excitation. Excitation nm selectively fragments into C7H7+ , whereas 400...

Computed potential energy surfaces of the nitrobenzene cation predict suitable excitation conditions for enhancing ion yield oscillations in time-resolved measurements.

This work explores Coulomb explosion (CE) dissociation pathways in multiply charged cations of para-nitrotoluene (PNT), a model compound for nitroaromatic energetic molecules. Experiments using strong-field ionization and mass spectrometry indicate that metastable PNT2+ PNT3+ undergo CE to produce NO2+ NO+. The experimentally measured kinetic energy release from upon formation NO+ agrees qualitatively with the predicted by computations reaction density functional theory (DFT). Both DFT...

Imipramine class tricyclic antidepressants have low ionization efficiencies that make them difficult to detect by using secondary ion mass spectrometry. Ultraviolet picosecond laser desorption postionization (ps-LDPI-MS) is examined here for the detection of four antidepressants: imipramine, desipramine, amitriptyline, and clomipramine. About 30 ps pulses at either 213 nm (5.8 eV) or 355 (3.5 are used samples under vacuum, 7.9 eV (157 nm) fluorine post-ionization, ions so formed detected...

Dissociation pathways of singly- and multiply charged gas-phase nitromethane cations were investigated with strong-field laser photoionization mass spectrometry density functional theory computations. There are multiple isomers the singly radical cation, several which can be accessed by rearrangement parent CH3-NO2 structure low energy barriers. While direct cleavage C-N bond from cation produces NO2+ CH3+, prior to dissociation accounts for fragmentation products including NO+, CH2OH+,...

The dynamics of the dimethyl methylphosphonate (DMMP) radical cation after production by strong field adiabatic ionization have been investigated. Pump-probe experiments using 1300 nm pulses to adiabatically ionize DMMP and a 800 non-ionizing probe induce coherent oscillations parent ion yield with period about 45 fs. yields two fragments, PO2C2H7+ PO2CH4+, oscillate approximately out phase ion, but slight shift relative each other. We use electronic structure theory nonadiabatic surface...