Penning ionization electron spectroscopy and photo-electron spectroscopy of molecular solids. II. Ammonia and water

The Penning ionization electron spectra (PIES) and ultraviolet photoelectron spectra (UPS) of ammonia and water molecules condensed on a cold metal substrate have been measured using thermal He*(2³S, 2¹S) metastable atoms and He(I) (58.4 nm) photons. The shifts of the observed positions of the PIES peaks relative to those of the UPS peaks in the condensed phase are roughly equal to the corresponding shifts in the gas phase. The relative intensities of the 3a₁ and 1e orbital peaks are reversed in the PIES and UPS for both gaseous and condensed ammonia; the origin of this reversal is interpreted as the difference between the interactions with metastable atoms and photons. On the other hand, the relative intensities of the 3a₁ orbital peak in the PIES and UPS for condensed water decrease as compared to the gas-phase spectra. This implies participation of the 3a₁ orbital of water in the hydrogen bonding.     

Angle resolved electron spectroscopy for measurement of surface segregation phenomena in liquids and solutions

The technique of variable take-off electron Spectroscopy is applied for the first time to the investigation of surface segregation phenomena in solutions. It is shown that this approach yields quantitative information on depth concentration profiles in electrolytic solutions. In particular, the mean segregation depth and the solute concentration at the solution-vacuum interface is obtained from measured relative intensity data. This is exemplified for the system tetrabutylammonium iodide in formamide.     

Structure and conformation of nitroxyl spin-label compounds in frozen solutions by electron nuclear double resonance spectroscopy

The structure and conformation of carboxylic acid, formyl, and propenoic acid derivatives of the nitroxyl spin-label 2,2,5,5-tetramethyl-1-oxypyrroline have been determined by electron nuclear double resonance (ENDOR) spectroscopy. From ENDOR spectra of the spin-label compounds in frozen solutions, we have assigned the resonance absorption features for each class of protons. The ENDOR spectra were analyzed on the basis of their dependence onH ₀. The maximum and minimum ENDOR shifts for each proton were shown to correspond to axially symmetric principal hyperfine coupling (hfc) components, from which the dipolar contributions were estimated to calculate electron-proton separations. Conformational analysis on the basis of torsion angle search calculations constrained by the ENDOR determined electron-proton distances revealed that in all three spin-label compounds the side chains are in a planar conformation with respect to the oxypyrrolinyl ring. In the carboxylic acid and formyl derivatives the C=O group is in as-trans conformation with respect to the vinyl group of the spin-label, while in the spin-labeled propenoic acid the conformation is found to be all planartrans-s-cis.     

Picosecond spectroscopy of dye solutions

Using picosecond spectroscopy technique the rotational relaxation time of rhodamine 4C in solutions both in the ground and excited states is measured to be the same and equal to 250 ps.

While anti-Stokes exciting of non-substituted rhodamine ethanol solution by a single 530 nm picosecond pulse, the blue shift of the gain spectrum on 6 nm over 350 ps after excitation was observed, the process being explained by the orientational solvate relaxation.     

Study of elastic electron collisions by plasma electron spectroscopy

In this work we study elastic electron collisions by using the plasma electron spectroscopy method, which is based on the study of the electron energy distribution function in a plasma afterglow. We give the results of this method for the electron-electron collision frequency, and the frequency and cross section of the elastic collision of electrons with helium atoms.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 7–11, February, 1987.In conclusion, the authors express their gratitude to Professor N. P. Penkin for useful discussions concerning this work.     

Conversion electron spectroscopy at IGISOL

Conversion elecron spectroscopy has been an important part of the nuclear spectrocopy research at the Department of Physics of the University of Jyväskylä since the commissioning of the first cyclotron in the mid 1970s. At the IGISOL facility a specialiced conversion electron spectrometer ELLI was developed in the late 1980s. The first results with ELLI were obtained using the beams from the old MC-20 cyclotron to study newly discovered isotopes of refractory fission products. In the present K130 cyclotron laboratory ELLI has been utilized in many decay-spectroscopy experiments both neutron-deficient and neutron-rich side of the valley of stability. In the early 2000s the new JYFLTRAP ion trap system overthrew ELLI from its permanent place in the IGISOL beamline. Conversion electron spectroscopy has continued with the new Penning trap that has been used in in-trap electron spectroscopy tests and post-trap electron spectroscopy is foreseen.     

Core photoelectron spectroscopy of some acetylenic molecules

Carbon 1s binding energies have been measured for CH₃CCH, CH₃CCCH₃, CF₃CCH and CF₃CCCF₃ and compared to a verified value for acetylene. Assignments are based on the application of a CNDO potential model with relaxation corrections which is quite successful in predicting binding energy shifts and upon qualitative considerations. Substitution of CF₃ groups shifts the acetylenic C 1s binding energy from 291.2 (HCCH) to 292.2 in CF₃CCH and 292.7 eV in CF₃CCCF₃. The unequal substitutional shifts are probably due to a saturation of substituent effect expected in competitive situations. With reservations arising from uncertainties in assignment due to lack of resolution, it appears that acetylenic C 1s binding energies decrease [to 290.7 (av.) in CH₃CCH and to 290.1 eV in CH₃CCCH₃] upon replacement of H by CH₃ groups. Although the decrease in acetylenic binding energies agrees with the chemical notion that CH₃ groups are electron donating with respect to unsaturated portions of the molecule, theoretical calculations available in the literature indicate that actual electron withdrawal or donation does not occur in these differently substituted molecules. The shifts of apparent binding energy correlate reasonably well with a ground state potential model which accounts for the effect of the charge on the adjacent atoms as well as on the photoionized atom. Even better correlation is obtained if the atomic potentials are corrected for electronic redistribution (relaxation) effects which occur during the photoionization process, and it is suggested that relaxation effects make a significant contribution to shifts of apparent binding energies. Surprisingly ground state potential and relaxation corrected potential calculations with the CNDO method suggest a large difference in C 1s binding energies of the two acetylenic carbon atoms in CH₃CCH which is not verified experimentally nor mirrored by calculations on CF₃CCH. The CH₃ binding energies are 291.8 eV in CH₃CCH and 291.3 eV in CH₃CCCH₃, both higher than values assigned to CH₄ or C₂H₆.     

Continuous X-ray-induced Auger electron spectroscopy

Bremsstrahlung emission from a tungsten anode has been used, for the first time, to obtain X-ray-induced Auger electron spectra (CXAES) in a conventional X-ray photoelectron spectrometer. Auger KLL signal and background intensities obtained from a silicon—aluminium sample have been compared with those obtained un der the same experimental conditions but using a standard aluminium anode. For such an aluminium anode, the respective contributions of the bremsstrahlung and the characteristic radiation to the C_KVV intensity have also been established.     

Mechanisms of charging in electron spectroscopy

From the use of physical arguments based on classical electrostatics and elementary solid state physics, the role of the various parameters involved in the charging mechanisms of insulating materials is analysed in detail when these insulating specimens are investigated by surface analytical techniques (mainly XPS and e⁻AES). The role of the sub-surface composition and structure is outlined and the strong correlations between charging effects and some radiation damage effects are pointed out. Some strategies are also deduced to minimise these effects.     

Auger electron spectroscopy of silicon surfaces

The measurements of the spectra of Auger electrons of the silicon surfaces performed at the pressure of (2–5)×10^?7 Torr are described. In this pressure range rapid oxidation and carbonization of the uppermost layers take place. The changes of characteristic energies in Auger and loss spectra are related to the change of chemical composition of the surface. The combination of the characteristic loss spectroscopy with Auger electron spectroscopy makes possible the determination of the chemical shifts. The measurements of the chemical shifts of the individual energy levels of the silicon atoms in both the pure and contaminated silicon surfaces, in quartz and Fe∶Si alloy are given. Finally, the possibilities and limitations of the heating for the silicon surface cleaning are examined.     

Determining the applicability boundaries of small-angle approximation solutions to the radiative transfer equation for elastic peak electron spectroscopy

The nonlinear term of the radiative transfer equation is considered in the small-angle approximation. Angular distributions of electrons elastically scattered from semi-infinite Au and Be samples are calculated. The error introduced by calculating flows of electrons elastically scattered from a semi-infinite target in the small-angle approximation is estimated.     

In-depth information from auger electron spectroscopy

In-depth information on impurity concentrations in the surface region of a solid can be obtained in a non-destructive way from Auger electron spectroscopy by varying the energy of the primary electrons. Examples are given for a silicon crystal covered by monolayers and multilayers of several types of impurity atoms.