Rydberg Electron Transfer Spectroscopy Research Articles

Electron attachment to strongly polar clusters

Electron localization is studied in formamide cluster anions. The isolated formamide molecule has a large dipole moment and its clusters can give birth to multipole-bound anions as well as valence anions. The vertical valence electron affinity of the isolated molecule is determined by electron transmission spectroscopy. The anion formation process is studied as a function of cluster size with Rydberg electron transfer spectroscopy. DFT calculations of the neutral and negatively-charged cluster structures show that the anion excess electron localizes on a single molecule. The adiabatic valence electron affinity of isolated formamide is deduced from the observation of the cluster size threshold for valence attachment.

Stabilization of the adenine covalent anion by micro-hydration: theoretical study

The Rydberg electron–transfer spectroscopy (RET) experiment [V. Periquet, A. Moreau, S. Carles, J.P. Schermann, C. Desfrançois, J. Electron. Spectrosc. Relat. Phenom., 106, 141 (2000)] showed that only after solvation by two water molecules the adenine molecule can form a stable covalent anion. Anions of adenine–water complexes containing different numbers of water molecules (A·W n , n =1–4) are investigated in this work with the use of quantum mechanical ab initio calculations. The calculations are used to determine the change of stability of the adenine covalent anion as the number of water molecules in the solvation shell increases. The analysis of the anion electron density is used to describe the localization of the excess electron in the A·W n complexes.

Isomerism of the anion of the indole–water dimer. Ab initio study

In our previous paper [J. Chem. Phys. 112, 3726 (2000)], the experimental group of Schermann, who participated in the study, reported a Rydberg electron transfer spectroscopy (RET) experiments concerning anions of the indole–water clusters. For [indole–(water)1]− the RET spectrum showed two peaks. Based on the ab initio calculations one of the peaks was assigned to a dipole–bound (DB) anion with a diffuse excess electron and it was speculated that the second peak could correspond either to an excited electronic state or an excited vibrational state of the DB anion. In this paper we present calculations that describe a second anion of the indole–water dimer where the excess electron is suspended between the indole and water molecules and also occupies a diffuse orbital. The relation of this finding to the RET spectrum is discussed and we propose assigning the two RET peaks to the two anions described in the calculations.

Structures of amide-water neutral complexes from dipole-bound anion formation

Using Rydberg Electron Transfer Spectroscopy, formation of dipole-bound anion complexes of formamide, N-methylformamide, N,N-dimethylformamide and N-methylacetamide with water has been studied. Each neutral complex can exist with several configurations and the lowest energy structures have been identified through comparison between Density Functional Theory calculations of the neutrals and measured electron binding energies of the observed weakly-bound anions.

Cluster size effects upon stability of adenine–methanolanions. Theoretical study

Rydberg electron transfer spectroscopy (RET) experiments [J. Electr. Spectr. Relat. Phenom. 106 (2000) 141] showed that only after being solvated with three methanol molecules the adenine molecule can form a stable covalent anion. Anions of adenine–methanol complexes (A·M n , n=1–3) are investigated in the present work with the use of quantum mechanical calculations. These complexes are good models to study how solvation affects the stability on the adenine anion. It is shown that among several hydrogen-bonded configurations of the A·M n , n=1−3, complexes there are systems which can form stable dipole-bound (DB) anions. These systems, however, are not the lowest energy structures. The stability of the covalent anion of A·M 3 is also investigated.

Nondissociative Electron Capture by Disulfide Bonds

By means of Rydberg electron-transfer spectroscopy (RETS), negative ion photoelectron spectroscopy (NIPES), and quantum chemistry calculations, we have studied electron attachment properties of a s...

Dipole-bound anion of 1,3-butanediol. Ab initio and Rydberg electron transfer spectroscopy study

Rydberg electron transfer spectroscopy (RET) has been used to determine the dipole-bound (DB) electron affinity (EA) of 1,3-butanediol and a single spectral feature was obtained corresponding to the EA value of 8±1 meV. A series of high-level ab initio calculations were also carried out for this system. They revealed an interesting configuration landscape of the 1,3-butanediol DB anion with four minima corresponding to different configurations. All four configurations can be responsible for the single RET spectral peak.

Dipole bound and valence state coupling in argon-solvated nitromethane anions

The coupling between the dipole bound and valence electronic states of the nitromethane anion has been investigated via Rydberg electron transfer spectroscopy and field detachment spectroscopy of the bare and argon-solvated anions. The unique aspects of the nitromethane system are highlighted by comparing the solvation behavior of nitromethane anion with that of acetonitrile, a system in which the dipole bound state is well-isolated from the resonance arising from excess electron occupation of its high lying lowest unoccupied molecular orbital.

Structures and electron affinities of indole–(water)N clusters

Rydberg electron transfer spectroscopy (RET) has been used to determine the dipole-bound electron affinity of the indole molecule, and the value of 3 meV was obtained. RET has also been employed to study [indole–(water)N]− cluster anions and the results have been interpreted with the help of ab initio calculations. It has been shown that for N=1 and 2 only dipole-bound anions are formed and that the electron attachment induces large amplitude motions in these systems. [Indole–(water)N]− anions with N=3 and 4 have not been observed. This finding for N=3 is consistent with a low theoretically predicted dipole moment of the neutral indole–(water)3 complex, which is insufficient for the formation of a stable dipole-bound anion. Above N=5, RET experiments showed formation of valence [indole–(water)N]− anions. From the observed size threshold for the formation of these anions, the negative value of the valence electron affinity of indole equal to −1.03±0.05 meV was deduced.

Cluster size effects upon anion solvation of N-heterocyclic molecules and nucleic acid bases

Abstract Rydberg electron transfer spectroscopy is used for the experimental determination of slightly negative electron affinities of N-heterocyclic molecules, pyridine, pyridazine, pyrimidine, pyrazine and DNA bases, adenine, cytosine, thymine and uracil. These molecules are solvated inside clusters of rare gases, water, ammonia or toluene in order to stabilize their anions against autodetachment, and the anion formation process is studied as a function of the number of solvent atoms or molecules. Determination of the cluster size thresholds above which valence anions are observed provides estimations of the electron affinities which are compared with the results of other experimental or theoretical determinations.

Experimental and theoretical ab initio study of the influence of N-methylation on the dipole-bound electron affinities of thymine and uracil

The influence of N-methylation on the dipole-bound electron affinities of pyrimidine nucleic acid bases, uracil and thymine, has been investigated theoretically using ab initio quantum mechanical calculations, and experimentally using Rydberg electron transfer spectroscopy. Both experiment and theory are consistent in showing that replacement of hydrogen atoms by methyl groups reduces electron affinities corresponding to formation of dipole-bound anions of these systems. Also, the distortion of the anion geometries with respect to the geometries of the neutral parents are reduced with the methylation.

Experimental and ab initio theoretical studies of electron binding to formamide, N-methylformamide, and N,N-dimethylformamide

The influence of methylation upon adiabatic electron affinities of formamide (F), N- methylformamide (NMF), and N,N-dimethylformamide (DMF) is experimentally investigated by means of Rydberg electron transfer spectroscopy and calculated with the use of high-level ab initio methods. In the anions of these systems the excess electrons are captured in diffuse dipole-bound states. The methylation of formamide results in a slight increase of the dipole moment and in an increased molecular size. The two factors have opposite effects on the electron affinity. Both experimental data and theoretical results are in agreement, showing that the molecular size effect dominates and that the electron affinity noticeably decreases with the methylation.