Ionization Potentials Of Atoms Research Articles

Do nonmetallic superalkali cations exist?

In order to explore the possibility of using hydrogen atoms as ligands in creating superalkalies, a systematic investigation on the F2H3+, O2H5+, N2H7+ and C2H9+ cations has been carried out. These nonmetallic cations have pretty low electron affinities (EA) of 3.55–4.48eV at the OVGF/6-311++G(3df, 3pd) level, and hence should be classified as superalkali cations. It is also worth mentioning that the weakly bound N2H7+ and C2H9+ cations exhibit even lower EA values than the ionization potential of Cs atom. In addition, the positive fragmentation energies indicate the stabilities of these cation species with respect to dissociation.

Measurement of the first ionization potential of astatine by laser ionization spectroscopy

The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to support the experimental result. The measured value serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of superheavy element 117, the heaviest homologue of astatine.

Is near-“spectroscopic accuracy” possible for heavy atoms and coupled cluster theory? An investigation of the first ionization potentials of the atoms Ga–Kr

Recent developments in ab initio coupled cluster (CC) theory and correlation consistent basis sets have ushered in an era of unprecedented accuracy when studying the spectroscopy and thermodynamics of molecules containing main group elements. These same developments have recently seen application to heavier inorganic or transition metal-containing species. The present work benchmarks conventional single reference coupled cluster theory (up to full configuration interaction for valence electron correlation and coupled cluster with up to full pentuple excitations (CCSDTQP) for core-valence correlation) and explicitly correlated coupled cluster methods [CC with single, double, and perturbative triple substitutions (CCSD(T)-F12)] for the atomic ionization potentials of the six 4p elements (Ga-Kr), a property with experimental error bars no greater than a few cm(-1). When second-order spin orbit coupling effects are included, a composite methodology based on CCSD(T) calculations yielded a mean signed error of just -0.039 kcal mol(-1) and a mean unsigned error of 0.043 kcal mol(-1). Inclusion of post-CCSD(T) correlation corrections reduced both of these values to -0.008 kcal mol(-1) and 0.025 kcal mol(-1), respectively, with the latter corresponding to an average error of just 9 cm(-1). The maximum signed error in the latter scheme was just -0.043 kcal mol(-1) (15 cm(-1)).

Survival window for atomic tunneling ionization with elliptically polarized laser fields

We find a fraction of atoms remain unionized after the laser pulse when the tunneled electrons are released in a certain window of initial field phase and transverse velocity. The survival window shifts with laser polarization ellipticity and its width varies with respect to laser intensity and atomic ionization potential. Neutral atom yield can be calculated by summing up tunneling probabilities in the window. Our theory can quantitatively reproduce the distribution of the survival yields vs laser ellipticity observed for helium in experiment. For other atom species with smaller ionization potential such as magnesium, our theory predicts a wider distribution than the strong-field approximation model while closer to the three-dimensional semiclassical electron ensemble simulations, indicating the important role of the Coulomb effects.

(e,2e) ionization studies of the stable noble gases in a coplanar symmetric geometry

A comprehensive set of coplanar symmetric ($e$,2$e$) ionization data are presented for the stable noble gas targets helium, neon, argon, krypton, and xenon. The incident electron energy ranged from 1.2 to 200 eV above the ionization potential of the target atoms, so as to span from near threshold to the high-energy regime. Data are presented with high precision, and cover a wide angular range from forward scattering where the electrons were detected at angles from 30\ifmmode^\circ\else\textdegree\fi{} to the incident electron beam, through to the backscatter region where the deflection angle was up to 130\ifmmode^\circ\else\textdegree\fi{}. The data are normalized to unity at each energy, and are compared to previously published theoretical calculations where available. The data show complex changes in the structure of the measured cross sections, depending upon both the energy and selected target. Similarities and differences in the cross sections were found between the different targets, which provide a challenge to future models of the ionization process.

Effect of gas species on THz generation from two-color lasers

The ionization current generated by two-color laser interaction with different gas atoms can produce strong terahertz (THz) emissions. The ionization potential of atoms determines the ionization rate. Thus, THz emission from different atoms varies. Particle-in-cell simulations are conducted to investigate the THz emission from He, Ne, Ar, and N. The THz emissions as a function of the laser field are different because the ionization rate and electron speed depend on the laser field and ionization potential.

Examining the heavy p-block with a pseudopotential-based composite method: Atomic and molecular applications of rp-ccCA

The relativistic pseudopotential variant of the correlation consistent composite approach (rp-ccCA) has been extended to lower p-block-containing molecules. The lower p-block is defined here as elements indium through iodine (In-I) and thallium through astatine (Tl-At). The accuracy of rp-ccCA has previously been established in a study of energetic properties of molecules containing 4p elements and thermodynamic data of 4d-containing molecules. In the current study, the atomic ionization potentials (IPs) and electron affinities (EAs) of In-I and Tl-At, as well as dissociation energies and enthalpies of formation of lower p-block mono-hydrides, mono-oxides, and dimers were determined with rp-ccCA. The compiled data set is referred to as the LP80 data set. The mean absolute deviation of the IPs and the EAs from the experimental data were 2.50 and 3.06 kcal mol(-1), respectively. Additionally, the total atomization energy for lead clusters (Pb(n), n = 2-6) was determined. For the lead clusters, a decrease in the total atomization energy was observed with the inclusion of spin-orbit coupling. The spin-orbit coupling of the molecules was determined with multireference configuration interaction, while scalar relativistic effects were accounted for within the pseudopotentials. The results obtained by rp-ccCA for the lower p-block support the utilization of the method in future studies where accurate energetic, spectroscopic, and thermodynamic data are necessary.

Femtosecond ionization and Coulomb explosion of small transition metal carbide clusters

Strong-field ionization and subsequent Coulomb explosion of small group 5 metal carbide clusters are explored using ultrashort pulses centered at 624nm. More efficient Coulomb explosion was observed according to: Ta>Nb>V due to the larger mass of tantalum, the slower cluster expansion times, and lower ionization potentials of large atoms. Minimum laser intensities required for the onset of each atomic charge state of V, Nb, and Ta were found to be nearly identical between metal carbides and previously observed group 5 metal oxide clusters indicating electron delocalization within the cluster. Ionization enhancement is explored by comparison to semi-classical tunneling theory.

Ionization potential and ion yield of CsM clusters sputtered from Si

We calculated the ionization potentials for 34 CsM molecules (where M is the element of the periodic table) by using SIESTA code, on the basis of the density functional theory. The calculated ionization potentials of CsM molecules were found essentially less than the ionization potentials of related atoms. Experimental SIMS relative sensitivity factors were found for the CsM+ cluster ions by using implanted standards. Exponential dependence between the relative sensitivity factors of CsM+ cluster ions and their ionization potentials was obtained. This lets us suggest that there is a direct emission of the CsM molecules during the cesium ion beam sputtering process; ionization of the CsM molecules occurs at the emitted surface because of the same mechanism as for sputtered atoms. Copyright © 2012 John Wiley & Sons, Ltd.

Use of photoelectron energy spectrum transfer equation for the measurement of a narrowband XUV pulse

To study the time evolution of a molecular state in an ultra-fast chemical reaction, the use of shorter pulses with higher photon energy and narrower bandwidth for both pump and probe is necessary. However, quick and precise measurement of their detailed time structures is a challenge. Over the last decade, great efforts have been made to measure an attosecond extreme ultraviolet (XUV) pulse. To date, several methods have been developed to measure the pulse duration and completely reconstruct it. The attosecond spectral phase interferometry for direct electric field reconstruction (SPIDER) and attosecond frequency-resolved optical gating (FROG) techniques are often used. However, these methods use state-of-the-art experimental set-ups and complicated data analysis procedures. To develop attosecond metrology for practical use (e.g. timing, measurement, evaluation, calibration, optimization, pumping, probing), we propose a quick and analytical method to precisely observe an attosecond XUV pulse with laser-assisted photo-ionization. The method is based on determining the laser-related phase of each streaked electron and using a transfer equation for one-step pulse reconstruction without any time-resolved measurements, iterative calculations, or data fitting procedures. Temporal errors of the pulse reconstruction are calculated from the XUV bandwidth. Because the transfer equation establishes a direct connection between the XUV pulse properties, the crucial laser parameters (peak intensity, phase, carrier envelope phase), the atomic ionization potential, and the measured photoelectron energy spectrum, we can use it to study any one of these properties from other known information and probe the dynamic processes of an ultra-fast reaction.

Microwave and optical breakdowns of gases and field harmonic generation

The gas breakdown in strong electromagnetic fields of microwave and optical frequency ranges is studied. Strong fields are understood as the fields in which the electron oscillation energy exceeds the ionization potential of gas atoms, but which are still weak for field ionization of atoms. In such fields, the inelastic collision frequency of electrons is higher than the elastic collision frequency. As a result, ionization of atoms is accompanied by efficient generation of high field harmonics.

Calculations of Metallofullerene Yields

The paper reports computations for Mg@C74, Ca@C74, Sr@C74, Ba@C74, and all lanthanoids, based on encapsulation into the only C 74 IPR (isolated pentagon rule) cage, and for Al@C 82 , Sc@C82, Y@C82 and La@C82 based on encapsulation into the IPR C2v C82 cage. Their structural and energetic characteristics are used for evaluations of the relative production yields, employing the encapsulation Gibbs-energy terms and saturated metal pressures. It is moreover shown that the encapsulation potential-energy changes in such series can be well related to the mere ionization potentials of the free metal atoms.

Delocalized electronic behavior observed in transition metal oxide clusters under strong-field excitation

Heterogeneously composed clusters are exposed to intensity resolved, 100 fs laser pulses to reveal the energy requirements for the production of the high charge states of both metal and nonmetal ions. The ionization and fragmentation of group V transition metal oxide clusters are here examined with laser intensities ranging nearly four orders in magnitude (∼3 × 10(11) W/cm(2) to ∼2 × 10(15) W/cm(2)) at 624 nm. The ionization potentials of the metal atoms are measured using both multiphoton ionization and tunneling ionization models. We demonstrate that the intensity selective scanning method can be utilized to measure the low ionization potentials of transition metals (∼7 eV). The high charge states demonstrate an enhancement in ionization that is three orders of magnitude lower in laser intensity than predicted for the atomic counterparts. Finally, the response from the various metals and the oxygen is compared to elucidate the mechanism of enhanced ionization that is observed. Specifically, the sequence of ion appearances demonstrates delocalized electron behavior over the entire cluster.

Raman Spectroscopy of the Reaction of Thin Films of Solid-State Benzene with Vapor-Deposited Ag, Mg, and Al

Thin films of solid-state benzene at 30 K were reacted with small quantities of vapor-deposited Ag, Mg, and Al under ultrahigh vacuum, and products were monitored using surface Raman spectroscopy. Although Ag and Mg produce small amounts of metal–benzene adduct products, the resulting Raman spectra are dominated by surface enhancement of the normal benzene modes from metallic nanoparticles suggesting rapid Ag or Mg metallization of the film. In contrast, large quantities of Al adduct products are observed. Vibrational modes of the products in all three systems suggest adducts that are formed through a pathway initiated by an electron transfer reaction. The difference in reactivity between these metals is ascribed to differences in ionization potential of the metal atoms; ionization potential values for Ag and Mg are similar but larger than that for Al. These studies demonstrate the importance of atomic parameters, such as ionization potential, in solid-state metal–organic reaction chemistry.

Ab initio calculations for XPS chemical shifts of poly(vinyl-trifluoroacetate) using trimer models

X-ray photoelectron spectra (XPS) of the polymer poly(vinyl-trifluoroacetate) show C(1s) binding energy shifts which are unusual because they are influenced by atoms which are several bonds away from the probed atom. In this work, the influence of the trifluoroacetate substituent on the 1s ionization potential of the carbon atoms of the polyethylene chain is investigated theoretically using mono-substituted, diad and triad models of trimers representing the polymer. Carbon 1s ionization energies are calculated by the Hartree–Fock theory employing Koopmans' theorem. The influence of the configuration and conformation of the functional groups as well as the degree of substitution are found to be important determinants of XPS spectra. It is further found that the 1s binding energy correlates in a linear fashion, with the total electrostatic potential at the position of the probe atom, and depends not only on nearest neighbor effects. This may have implications for the interpretation of high-resolution XP spectra.

Valence universal multireference coupled cluster calculations of the properties of indium in its ground and excited states

In view of its importance in high precision spectroscopy, the valence universal multireference coupled cluster (VU-MRCC) method with four-component relativistic spinors has been applied to compute ionization potential (IP) and excitation energies (EEs) of the indium atom (In I). The effect of electron correlations on the ground and excited state properties is investigated using different levels of CC approximations and basis sets. This study reveals that for a given basis, the linearized VU-MRCC method tends to underestimate the IP, EEs and other one-electron properties such as magnetic hyperfine constant (A) compared to the full blown VU-MRCC method. Our computed results have been compared with available theoretical and experimental data. The IP, EEs, A and oscillator strengths (f) determined at the VU-MRCC level are in excellent agreement with the experimental results. The properties reported here further demonstrate that a basis set with at least h-type of orbitals is ubiquitous to achieve converged results.

Metallofullerene Series: Free-Metal Ionization-Potential Control of the Production Yields

The paper reports computations for Al@C 82 , Sc@C 82 , Y@C 82 and La@C 82 based on encapsulation into the IPR (isolated pentagon rule) C 2 υ C 82 cage and also on Mg@C 74 , Ca@C 74 , Sr@C 74 and Ba@C 74 based on encapsulation into the only C 74 IPR cage. Their structural and energetic characteristics are used for evaluations of the relative production yields, employing the encapsulation Gibbs-energy terms and saturated metal pressures. It is shown that the results can be well re- lated to the ionization potentials of the free metal atoms.

Enhancement of Laser-Induced Fluorescence by Intense Terahertz Pulses in Gases

The enhancement of laser-induced fluorescence by intense terahertz pulses was studied both theoretically and experimentally using selected gases. Semiclassical physical picture incorporating photoionization, electron heating, impact excitation, and dissociative recombination was used to explain the plasma dynamics under terahertz radiation in picosecond scale. The dependences of enhanced fluorescence on the terahertz field, laser intensity, and atomic properties were systematically investigated with neon, argon, krypton, xenon, methane ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{CH}_{4}$</tex></formula> ), ethane ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX"> $\hbox{C}_{2}\hbox{H}_{6}$</tex></formula> ), propane ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{C}_{3}\hbox{H}_{8}$ </tex></formula> ), and n-butane ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX"> $\hbox{C}_{4}\hbox{H}_{10}$</tex></formula> ) gases. In noble gas plasma, both narrow line emission and broad continuum emission were found to be enhanced by the terahertz field. Their enhancement ratios and time-dependent enhanced fluorescence are greatly influenced by the scattering cross section and ionization potential of atoms. In alkane gas plasma, the enhancement of the fluorescence emission from various molecular fragments was also observed.

Dynamics of photo-activated Coulomb complexes

Intense light with frequencies above typical atomic or molecular ionization potentials as provided by free-electron lasers couples many photons into extended targets such as clusters and biomolecules. This implies, in contrast to traditional multi-photon ionization, multiple single-photon absorption. Thereby many electrons are removed from their bound states and either released or trapped if the target charge has become sufficiently large. We develop a simple model for this photo-activation to study electron migration and interaction. It satisfies scaling relations that help to relate quite different scenarios. Understanding this multi-electron dynamics on very short time scales is vital for assessing the radiation damage inflicted and for paving the way to coherent diffraction imaging of single molecules.

Model of pulsed electric discharge expansion in dense gas, taking into account electron and radiative thermal conductivities. IV. Limiting brightness of discharge radiation

Based on the relation between the radiation brightness BR of the pulsed high-current electric discharge in dense gas (Xe, Kr, Ar, Ne, He, N2, and air at atmospheric pressure and above) and its temperature, the dependence of the limiting brightness BLIM of discharge channel radiation on ionization potentials of atoms of mentioned gases was obtained, and the condition under which the brightness saturation is achieved was determined. It was shown that this dependence is in agreement with experimental data of various researchers.