Several new molecular anions, in their dipole-bound ground states, have been created by charge exchange between polar molecules and laser-excited Rydberg atoms. Measurement of electron-binding energies, means electric field detachment, as function known dipole moments gives the first experimental estimation minimum required to bind an electron.

Uracil, thymine, and adenine anions were produced in charge-exchange collisions with laser-excited Rydberg atoms. Anion creation rates for uracil thymine exhibit electron energy dependences which are interpreted as due to the of both dipole-bound conventional (valence) while only observed adenine.

Ground-state dipole-bound anions are fragile molecular species which excess electrons almost entirely located in a very diffuse orbital outside the frame. They can be created by attachment of low energy to polar molecules or small clusters dipole moments larger than practical critical value 2.5 D. present analogies with Rydberg atoms and their geometrical structures nearly identical those neutral parents. Experimentally, dipole-binding systems is non-perturbative reversible ionization...

Conventional (valence) and dipole-bound anions of the nitromethane molecule are studied using negative ion photoelectron spectroscopy, Rydberg charge exchange field detachment techniques. Reaction rates for between Cs(ns,nd) Xe(nf ) atoms with CH3NO2 exhibit a pronounced maximum at an effective quantum number n*≊13±1 which is characteristic formation [μ(CH3NO2)=3.46 D]. However, breadth (Δn≊5, FWHM) n-dependence reaction rate also interpreted to be indicative direct attachment into valence...

We studied the photoionization of 2-pyridone and its tautomer, 2-hydroxypyridine by means VUV synchrotron radiation coupled to a velocity map imaging electron/ion coincidence spectrometer. The efficiency (PIE) spectrum is composed steps. state energies [2-pyridone]+ cation in ground à excited electronic states, as well [2-hydroxypyridine]+ state, are determined. slow photoelectron spectra (SPES) dominated 000 transitions corresponding states together with several weaker bands population pure...

Rydberg electron attachment to gas-phase isolated uracil molecules and mixed uracil−argon clusters is examined in a crossing beam experiment. By means of reproducible conditions, it possible control the electron-binding process, which strongly influenced by solvation. Attachment followed evaporation single argon atom already sufficient switch from dipole-bound valence monomer anions, as demonstrated field-detachment measurements. The existence both types anions good agreement with two...

Deactivation pathways of electronically excited states have been investigated in three protonated aromatic amino acids: tryptophan (Trp), tyrosine (Tyr) and phenylalanine (Phe). The acids were generated by electrospray with a 266 nm femtosecond laser, the subsequent decay being monitored through fragmentation ions induced and/or enhanced another pulse at 800 nm. state TrpH+ decays 380 fs gives rise to two channels: hydrogen atom dissociation or internal conversion (IC). In TyrH, is slowed...

The first study of very low energy electron attachment to mixed water-ammonia clusters is reported here. A ``magic'' cluster anion distribution with strong similarities that pure water anions observed. (${\mathrm{H}}_{2}$O . .${\mathrm{NH}}_{3}$${)}^{\mathrm{\ensuremath{-}}}$ dimer created under specific experimental conditions and its existence a test the theory binding by dipole. This fragile species has small as inferred from field detachment experiments.

We describe two simple models for the determination of electron binding energies (${\mathit{E}}_{\mathit{b}}$) several dipole-bound negative ions from field-detachment experiments and charge-transfer formation-rate-constant measurements in collisions between cold neutral molecules Rydberg atoms. These are able to correctly reproduce experimental data, which we deduce compatible sets ${\mathit{E}}_{\mathit{b}}$ values. A curve-crossing model calculating anion formation rate constants allows...

The gas-phase structures of protonated peptides are studied by means resonant infrared multiphoton dissociation spectroscopy (R-IRMPD) performed with a free electron laser. peptide and protonation sites obtained through comparison between experimental IR spectra their prediction from quantum chemistry calculations. Two different analyses conducted. It is first supposed that only well-defined conformations, sufficiently populated according to Boltzmann distribution, contribute the observed...

Molecular assemblies held together by weak intermolecular bonds exhibit a rich variety of geometries. Even simple complex formed only two molecules can adopt several conformations corresponding to different geometrical isomers. Isomers small polar dimers be isolated nondestructively taking advantage selective and reversible ionization process, with the use mass spectrometry method that allows determination control configuration neutral or negatively charged molecular complexes in supersonic...

Protonated tryptophan ions (TrpH+) are generated by electrospray ionization and dissociated irradiation with a UV laser. Different photo-fragments observed among which new photo-induced dissociation channel leading to the loss of hydrogen atom that is not in conventional collision-induced dissociation. A radical cation (Trp+) produced this process subsequently leads m/z = 130 fragment through Cα–Cβ bond cleavage, typical fragmentation product Trp+ either electron impact or photo-ionization....

Nitrobenzene anions (NB−) in both valence and dipole bound states are examined using laser (photodetachment) photoelectron Rydberg electron transfer (RET) spectroscopies. Photoelectron spectroscopy of the NB− anion yields a (adiabatic) affinity 1.00±0.01 eV. The reaction rates for charge between atoms cesium xenon high [Cs(ns,nd) Xe(nf )] NB exhibit prominent peak their n-dependencies consistent with formation having an 28 meV. Para-dinitrobenzene (pDNB) has zero moment large quadrupole...

Dipole-bound anions of 27 molecules containing either a carbonyl, nitrile, or sulfoxide group were studied using Rydberg electron transfer (RET) reactions with rubidium atoms excited to ns 2S and nd 2D states. The affinity each molecule was obtained from the state, nmax*, that gave largest negative ion yield empirical relationship affinity=23/nmax*2.8 eV as well fitting charge exchange profile theoretical curve crossing model. Electron affinities for low dipole moment (carbonyls) also...

Protonated dialanine cations have been isolated in a Fourier transform ion cyclotron resonance mass-spectrometer (FT-ICR-MS) and subjected to infrared multiphoton dissociation (IRMPD) at the free electron laser facility CLIO Orsay (France). The spectral dependence of IR induced fragmentation pattern mid-infrared region (800–2000 cm−1) is interpreted with help structure vibrational spectrum calculations different protonated conformers. This comparison allows for assignment proton on terminal...

The relative formation rates of negative water clusters have been measured as a function electron energy in the 8–170 meV range. source is beam xenon atoms laser-excited Rydberg states. Strong dependences are observed for attachment dimer, hexamer, and heptamer.

Finite temperature Car−Parrinello molecular dynamics simulations are performed for the protonated dialanine peptide in vacuo, relation to infrared multiphoton dissociation experiments. The emphasize flexibility of different torsional angles at room and dynamical exchange between conformers which were previously identified as stable 0 K. A proton transfer occurring spontaneously N-terminal side is also observed characterized. theoretical absorption spectrum computed from dipole time...

DNA oligonucleotide ions forming G-quadruplex structures were studied in the gas phase using IRMPD spectroscopy. Data interpretation on these large biomolecule was made carefully chosen control experiments. The major finding is a fingerprint of hydrogen bonding guanine C6O6 stretching mode that allows probing conservation G-quartets phase. experiments demonstrate bonds human telomeric sequence d(TTAGGG)4.

An experimental method for the discrimination between nearly degenerate isomers of size selected clusters closed-shell polar molecules is presented. It based upon electron attachment properties dipole fields since a minimum value (≊2.5 D) molecular dipoles required binding. When neutral are created in different configurations only those with large enough resulting moments bind electrons and give birth to stable anions. These dipole-bound anions have geometries their parents which here...

We study charge transfer collisions between laser-excited xenon (nf, np) Rydberg atoms and acetonitrile molecules clusters. CH3CN- (CH3CN)3- anions are observed only in extremely narrow ranges of n-values. The measurement the electron binding energies these shows that they dipole-bound states. transition to solvated behaviour corresponds appearance more strongly bound large (N > 10) which created for a wide range Rydberg-electron energies.

The prediction accuracy of second-order Moller-Plesset theory MP2 and density functional DFT-(D) with without empirical dispersion correction within the resolution identity approximation (ri) have been investigated for assignment infrared spectra gas-phase peptides. A training set 17 conformers phenylalanine containing capped peptides used to establish mode-specific local scaling factors. Inclusion terms at DFT level turns significantly improve predicted IR spectra. At DFT-D level, nonhybrid...