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Molecular modification induced through the resonant attachment of a low energy electron (LEE) is a novel approach for molecular engineering. In this communication, we explore the possibility to use the LEE as a quantum tool for the in situ preparation of short lived molecules. Using ab initio quantum chemical methods, this possibility is best illustrated for the in situ preparation of the intrinsically short-lived carbon-carbon covalent dimer of CO from a glyoxal molecule. The chemical conversion of glyoxal to the covalent dimer of CO is initiated and driven by the resonant capture of a near 11 eV electron by the glyoxal molecule. The resulting two-particle one-hole (2p-1h) negative ion resonant state (NIRS) of the glyoxal molecule undergoes a barrierless radical dehydrogenation reaction and produces the covalent dimer of CO. The autoionization electron spectra from the 2p-1h NIRS at the dissociation limit of the dehydrogenation reaction provides access to the electronic states of the CO dimer. The overall process is an example of a catalytic electron reaction channel [ABSTRACT FROM AUTHOR]

An extensive calculation on the effects of spacer length enhancement on the second-order nonlinear optics (NLO) properties of dipolar molecules connected by the CH2 groups is performed. The molecules exhibit a very strong odd-even behavior in the first hyperpolarizabilities, which are reported experimentally on similar systems but the origin of such phenomena remains unclear.

Dissociative electron attachment (DEA) to acetone is studied in terms of the absolute cross section for various fragment channels in the electron energy range of 0-20 eV. H- is found to be the most dominant fragment followed by O- and OH- with only one resonance peak between 8 and 9 eV. The DEA dynamics is studied by measuring the angular distribution and kinetic energy distribution of fragment anions using Velocity Slice Imaging technique. The kinetic energy and angular distribution of H- and O- fragments suggest a many body break-up for the lone resonance observed. The ab initio calculations show that electron is captured in the multi-centered anti-bonding molecular orbital which would lead to a many body break-up of the resonance. [ABSTRACT FROM AUTHOR]

The resonance capture of ubiquitous very low energy electrons (vLEEs) into the π* orbitals of nucleobases is a potential doorway to DNA damage. Our ab initio quantum chemical calculations reveal a possible protection function, which is specific to the complementary basepairing, against such vLEE induced DNA damage. [ABSTRACT FROM AUTHOR]

Static polarizability and first- and second-order hyperpolarizability tensors are computed at the correlated level for a series of para-nitroaniline derivatives. The importance of including electron correlation effects in the determination of equilibrium structure and the molecular properties is investigated.

Remarkable site-specificity in the resonant attachment of low energy electrons (LEEs) to molecular targets is proposed as an efficient method for inducing chemical reactivity on specific sites of molecules. The Coulomb interaction between the attached electron and the most polarizable molecular electrons localized on the attached site is the reason for site-specific chemical reactivity. The Coulombically induced site-specific chemical reactivity is best illustrated by the LEE induced chemical transformation of a weakly bound molecular complex into a strong covalent adduct. The chemical transformation occurs due to the Coulombically induced nucleophilicity on a specific molecular moiety in the complex. A simple strategy for inducing site-specific chemical reactivity using a LEE may find new avenues in chemical synthesis. [ABSTRACT FROM AUTHOR]

Using a low energy electron (LEE) as a catalyst, the electronic origin of the catalytic strategies corresponding to substrate selectivity, reaction specificity and reaction rate enhancement is investigated for a reversible unimolecular elementary reaction. An electronic energy complementarity between the catalyst and the substrate molecule is the origin of substrate selectivity and reaction specificity. The electronic energy complementarity is induced by tuning the electronic energy of the catalyst. The energy complementarity maximizes the binding forces between the catalyst and the molecule. Consequently, a new electronically metastable high-energy reactant state and a corresponding new low barrier reaction path are resonantly created for a specific reaction of the substrate through the formation of a catalyst-substrate transient adduct. The LEE catalysis also reveals a fundamental structure-energy correspondence in the formation of the catalyst-substrate transient adduct. Since the energy complementarities corresponding to the substrate molecules of the forward and the backward steps of the reversible reactions are not the same due to their structural differences, the LEE catalyst exhibits a unique one-way catalytic strategy, i.e., the LEE catalyst favors the reversible reaction more effectively in one direction. A characteristic stronger binding of the catalyst to the transition state of the reaction than in the initial reactant state and the final product state is the molecular origin of barrier lowering. [ABSTRACT FROM AUTHOR]

Ab initio quantum chemical studies show that a very weak molecular complexation of CO2 with a dipolar molecule is able to suppress the autoionization of the electron from its transient negative ion states. Since the autoionization is suppressed, the transient negative ion can efficiently relax its geometry to form the reductively activated CO2 moiety. Unlike the reductively activated isolated CO2 molecules, which are deactivated immediately due to their thermodynamic metastability, the reductively activated CO2 moieties of the weak molecular complexes are infinitely long-lived and, hence, permanently reactive. [ABSTRACT FROM AUTHOR]

O− desorbed from amorphous and crystalline films of CO2 at 18 K under low energy electron impact is studied using time of flight mass spectrometry. The nature of the CO2 film is characterized by Fourier transform infrared spectrometry as a function of film thickness. It is found that the desorption rate from amorphous films is considerably larger than that from crystalline films. The desorption signal from the 4 eV resonance is found to be the dominant one as compared to that from the higher energy resonances, notably the one at 8 eV observed in the gas phase. This is explained in terms of the large enhancement in the dissociative electron attachment cross section for the 4 eV resonance in the condensed phase reported earlier using the charge trapping method. [ABSTRACT FROM AUTHOR]

The article reports on the research of hepatocellular carcinoma and cholangiocellular carcinoma in a duck.