Photon-stimulated Desorption Research Articles

Enhancement effect in photon-stimulated ion desorption for benzene adsorbed on silicon surfaces observed using angle-dependent technique

We have investigated photon-stimulated ion desorption from deuterated benzene (C 6D 6) adsorbed on Si(1 0 0) and Si(1 1 1) surfaces following C 1s core excitation. Using time-of-flight mass spectrometry combined with angle-dependent technique, we measured the dependences of mass-spectra of desorption ions on photon energies and on incident angle ( θ) of synchrotron beam. We have found the ion yields for adsorbate-derived fragments of CD + and CD 2 + are enhanced in very small angles of incident X-rays. Moreover, molecular orientation effect appeared in excitation energy dependences of D + ions from the Si(1 0 0) and Si(1 1 1) surfaces; that is, ion yield spectra measured at θ = 10° are different from that at θ = 65°. Furthermore, it was found that desorption ion yields increase greatly with decreasing incident angles. The angular dependences are consistently similar for all ion species, excitation energies, and indexes of substrates. Possible desorption processes are described on the basis of the observations.

Transport of nonmethane hydrocarbons to Jupiter's troposphere by descent of smog particles

Ethane and other C 2 and C 3 nonmethane hydrocarbons were observed by the Galileo Probe Mass Spectrometer to have a deep minimum in mixing ratio near and below the tropopause, rising to much larger values at and below the 15 bar level. This minimum requires that these hydrocarbons condense on smog particles at low temperatures. The large amounts at deeper levels were produced in the pumping system of the instrument and any contribution from the ambient atmosphere cannot be resolved, although evaporation from the smog particles is proposed and incorporated in a model. In the stratosphere some of the ethane is released by photon-stimulated desorption. The other light nonmethane hydrocarbons are not modeled, but can be expected to show the same behavior as ethane.

Processes that Promote and Deplete the Exosphere of Mercury

It has been speculated that the composition of the exosphere is related to the composition of Mercury’s crustal materials. If this relationship is true, then inferences regarding the bulk chemistry of the planet might be made from a thorough exospheric study. The most vexing of all unsolved problems is the uncertainty in the source of each component. Historically, it has been believed that H and He come primarily from the solar wind (Goldstein, B.E., et al. in J. Geophys. Res. 86:5485–5499, 1981), Na and K come from volatilized materials partitioned between Mercury’s crust and meteoritic impactors (Hunten, D.M., et al. in Mercury, pp. 562–612, 1988; Morgan, T.H., et al. in Icarus 74:156–170, 1988; Killen, R.M., et al. in Icarus 171:1–19, 2004b). The processes that eject atoms and molecules into the exosphere of Mercury are generally considered to be thermal vaporization, photon-stimulated desorption (PSD), impact vaporization, and ion sputtering. Each of these processes has its own temporal and spatial dependence. The exosphere is strongly influenced by Mercury’s highly elliptical orbit and rapid orbital speed. As a consequence the surface undergoes large fluctuations in temperature and experiences differences of insolation with longitude. Because there is no inclination of the orbital axis, there are regions at extreme northern and southern latitudes that are never exposed to direct sunlight. These cold regions may serve as traps for exospheric constituents or for material that is brought in by exogenic sources such as comets, interplanetary dust, or solar wind, etc. The source rates are dependent not only on temperature and composition of the surface, but also on such factors as porosity, mineralogy, and space weathering. They are not independent of each other. For instance, ion impact may create crystal defects which enhance diffusion of atoms through the grain, and in turn enhance the efficiency of PSD. The impact flux and the size distribution of impactors affects regolith turnover rates (gardening) and the depth dependence of vaporization rates. Gardening serves both as a sink for material and as a source for fresh material. This is extremely important in bounding the rates of the other processes. Space weathering effects, such as the creation of needle-like structures in the regolith, will limit the ejection of atoms by such processes as PSD and ion-sputtering. Therefore, the use of laboratory rates in estimates of exospheric source rates can be helpful but also are often inaccurate if not modified appropriately. Porosity effects may reduce yields by a factor of three (Cassidy, T.A., and Johnson, R.E. in Icarus 176:499–507, 2005). The loss of all atomic species from Mercury’s exosphere other than H and He must be by non-thermal escape. The relative rates of photo-ionization, loss of photo-ions to the solar wind, entrainment of ions in the magnetosphere and direct impact of photo-ions to the surface are an area of active research. These source and loss processes will be discussed in this chapter.

Soft x-ray photoreactions of CF3Cl adsorbed on Si(111)-7×7 studied by continuous-time photon-stimulated desorption spectroscopy near F(1s) edge

The continuous-time core-level photon-stimulated desorption (PSD) spectroscopy was employed to monitor the monochromatic soft x-ray-induced reactions of CF3Cl adsorbed on Si(111)-7x7 near the F(1s) edge (681-704 eV). Sequential F+ PSD spectra were measured as a function of photon exposure at the CF3Cl-covered surface (dose=0.3x10(15) molecules/cm2, approximately 0.75 ML). The F+ PSD and total electron yield (TEY) spectra of molecular solid CF3Cl near the F(1s) edge were also measured. Both F+ PSD and TEY spectra show two features at the energy positions of 690.2 and 692.6 eV, and are attributed to the excitations of F(1s) to 11a1[(C-Cl)*] and (8e+12a1)[(C-F)*] antibonding orbitals, respectively. Following Auger decay, two holes are created in the F(2p) lone pair and/or C-F bonding orbitals forming the 2h1e final state which leads to the F+ desorption. This PSD mechanism, which is responsible for the F+ PSD of solid CF3Cl, is employed to interpret the first F+ PSD spectrum in the sequential F+ PSD spectra. The variation of spectrum shapes in the sequential F+ PSD spectra indicates the dissipation of adsorbed CF3Cl molecules and the formation of surface SiF species as a function of photon exposure. From the sequential F+ PSD spectra the photolysis cross section of the adsorbed CF3Cl molecules by photons with varying energy (681-704 eV) is determined to be approximately 1.0x10(-17) cm2.

The Dust and Gas Around β Pictoris

We have obtained Spitzer IRS 5.5-35 μm spectroscopy of the debris disk around β Pictoris. In addition to the 10 μm silicate emission feature originally observed from the ground, we also detect the crystalline silicate emission bands at 28 and 33.5 μm. This is the first time that the silicate bands at wavelengths longer than 10 μm have ever been seen in the β Pictoris disk. The observed dust emission is well reproduced by a dust model consisting of fluffy cometary and crystalline olivine aggregates. We searched for line emission from molecular hydrogen and atomic [S I], Fe II, and Si II gas but detected none. We place a 3 σ upper limit of <17 M⊕ on the H2 S(1) gas mass, assuming an excitation temperature of Tex = 100 K. This suggests that there is less gas in this system than is required to form the envelope of Jupiter. We hypothesize that some of the atomic Na I gas observed in Keplerian rotation around β Pictoris may be produced by photon-stimulated desorption from circumstellar dust grains.

Selective chemical bond breaking characteristically induced by resonant core excitation ofester compounds on a surface

Inner-shell excitation possesses an attractive potential to induce selective chemical bondbreaking due to its special localization and atomic selectivity. This paper reviews our recentworks about site-selective (or site-specific) photon stimulated desorption (PSD) ofcore-excited ester compounds, poly(methyl methacrylate) (PMMA) thin films, condensedmethyl isobutyrate (MIB) multilayers, methyl ester terminated self-assembled monolayers(SAMs), partially deuterided SAMs and ethyl ester terminated SAMs. Exact selective bondbreaking was observed for all molecular systems except for MIB multilayers: COO–R(R = CH3,C2H5) breaking in the , O 1s(OR) excitations and CO–OR in the excitation. Such resonant excitations take place within the functional group locally andthe initial memory of the excited site and its localization character is effectivelyconserved during the PSD process even after subsequent Auger decays and ionicdissociation/desorption. Variation of selectivity observed here indicates the importanceof the molecular environment and the contribution of the indirect dissociationprocess due to statistical energy relaxation and x-ray-induced electron stimulateddesorption. The obvious polarization dependence measured only for selectivelydesorbing ions also supports the above characteristics. Neutral fragments desorbingfrom core-excited PMMA follow the profile of the total electron yield spectrumbut not the partial ion yield of corresponding ions. This result indicates thationic dissociation locally promoted by Coulomb repulsion plays an important roleto reveal site-selectivity in chemical reactions induced by core-level excitation.

Alkali halide decomposition and desorption by photons—the role of excited point defectsand surface topographies

Our recent work on photon-stimulated desorption of alkali halide surfaces has beenreviewed. Most of the experimental data are presented for the first time. This new materialis supplemented with two examples of our work published previously (see Szymonski et al 1996 Surf. Sci. 363 229; 2002 Acta Phys. Pol. 33 2237). The results are discussed andcompared with relevant experimental and theoretical work by other authors. In particular,we focus on two aspects of the studies: high resolution AFM imaging of desorbed surfaces,and measurements of mass selected fluxes of the desorbing atoms. It is foundthat, at initial stages of the UV-photon stimulated desorption, the process isoccurring in a ‘layer-by-layer’ mode as a result of growth and linking of monatomicpits on the surface. This results in periodic changes of surface topography fromatomically flat to rough with a period equal to the time needed for desorption of1 ML. Such periodic changes of the surface topography affect the efficiency of thedesorption and result in oscillatory dependence of the emitted particle yieldsversus photon fluence. Careful analysis of the yields reveals that during irradiationthere is a substantial number of stable ground state F-centres accumulated underthe surface. The number of accumulated defects is changing periodically withthe photon fluence in anti-correlation with the desorption yields. Based on thementioned results, we argue that the production of F-centres and their interaction withthe surface are, in fact, the limiting factor for PSD. To test the validity of thisstatement a series of desorption experiments for the crystal co-irradiated withvisible light (with a wavelength corresponding to the F-centre absorption band)and UV photons have been performed. A dramatic increase in the desorptionyield, as well as pronounced changes in the surface erosion process, have beenfound.

Continuous-time core-level photon-stimulated desorption spectroscopy for monitoring soft x-ray-induced reactions of molecules adsorbed on a single-crystal surface

Continuous-time core-level photon-stimulated desorption (PSD) spectroscopy was proposed for monitoring the soft x-ray-induced reactions of molecules adsorbed on a single-crystal surface. Monochromatic synchrotron radiation was used as a soft x-ray light source in the photon-induced reactions of $\mathrm{C}{\mathrm{F}}_{3}\mathrm{Cl}$ adsorbed on a $\mathrm{Si}(111)\text{\ensuremath{-}}7\ifmmode\times\else\texttimes\fi{}7$ surface at $30\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and also as a probe for studying the produced fluorination states of the bonding surface Si atom in the positive-ion PSD spectroscopy. The ${\mathrm{F}}^{+}$ PSD spectrum was obtained by monitoring the ${\mathrm{F}}^{+}$ signal as a function of incident photon energy near the $\mathrm{Si}(2p)$ edge $(98--110\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$. Sequential ${\mathrm{F}}^{+}$ PSD spectra were measured as a function of photon exposure at four adsorbate coverages (the first $\text{dose}=0.3\ifmmode\times\else\texttimes\fi{}{10}^{15}\phantom{\rule{0.3em}{0ex}}\text{molecules}∕{\mathrm{cm}}^{2}$, the second $\text{dose}=0.8\ifmmode\times\else\texttimes\fi{}{10}^{15}\phantom{\rule{0.3em}{0ex}}\text{molecules}∕{\mathrm{cm}}^{2}$, the third $\text{dose}=2.2\ifmmode\times\else\texttimes\fi{}{10}^{15}\phantom{\rule{0.3em}{0ex}}\text{molecules}∕{\mathrm{cm}}^{2}$, and the fourth $\text{dose}=3.2\ifmmode\times\else\texttimes\fi{}{10}^{15}\phantom{\rule{0.3em}{0ex}}\text{molecules}∕{\mathrm{cm}}^{2}$). For the first and second $\mathrm{C}{\mathrm{F}}_{3}\mathrm{Cl}$-dosed surfaces, the sequential ${\mathrm{F}}^{+}$ PSD spectra show the variation of their shapes with photon exposure and indicate the formation of surface SiF species. The sequential ${\mathrm{F}}^{+}$ PSD spectra for the third and fourth $\mathrm{C}{\mathrm{F}}_{3}\mathrm{Cl}$-dosed surfaces also show the variation of their shapes with photon exposure and depict the production of surface SiF and $\mathrm{Si}{\mathrm{F}}_{3}$ species.

Photon-stimulated desorption from chlorinated Si(111): Etching of SiCl by picosecond-pulsed laser irradiation

Cl etching of silicon surfaces assisted with short pulsed laser irradiation is analyzed to find out chloride removal processes without using thermal reaction. When a Cl-saturated Si(111) surface was irradiated by a picosecond pulsed laser at 400 nm, desorptions of SiCl and $\mathrm{Si}{\mathrm{Cl}}_{2}$ molecules were observed with a quadrupole mass spectrometer with a pulse-counting system. The presence of the SiCl desorption shows previously unfound etching process without thermally induced recombinative reaction. Time-of-flight and signal-ratio of the SiCl and $\mathrm{Si}{\mathrm{Cl}}_{2}$ molecules indicated that they were assigned to products from restatom monochlorides and adatom polychlorides, respectively. High desorption rates of the chlorides which depend on laser fluence nonlinearly suggest that multiple excitation by substrate hot carriers is essential to the etching.

X-ray absorption fine structure and photon-stimulated ion desorption from solid MoO 3 at molybdenum 3p 1/2, 3p 3/2 and oxygen 1s edges

We investigated photon-stimulated ion desorption (PSID) from solid MoO 3 following Mo 3p 1/2, 3p 3/2 and O 1s inner-shell excitations. The photon-energy dependences of O + ion desorption yields were measured using quadrupole mass spectrometry. Near-edge X-ray absorption fine structure (NEXAFS) spectra were measured by the total electron yield method and were compared with the desorption yield curves. Relatively high desorption yields were observed in O 1s → e g resonance compared with that in O 1s → t 2g resonance, while no enhanced yields were observed in either the Mo 3p 1/2 or Mo 3p 3/2 edge. The enhancement effect in the O 1s → e g resonance was attributed to fast bond breakage induced by the antibonding nature of the σ ∗-like e g orbital. On the other hand, the non-enhancement following the Mo 3p 1/2 and 3p 3/2 edges was ascribed to the de-excitation of the excited electrons via very fast Coster–Kronig transitions, which can take place only following Mo 3p 1/2 and 3p 3/2 excitations.

Observation of the sodium exosphere from mercury magnetospheric orbiter

The Mercury Sodium Atmosphere Spectral Imager (MSASI) in the BepiColombo mission will address a wealth of fundamental scientific questions pertaining to the Mercury’s exosphere. Together, our measurements on the overall scale will provide ample new information on regolith–exosphere–magnetosphere coupling as well as new understanding of the dynamics governing the ‘surface-bounded exosphere’. It arises quite clearly from ground-based observations that the regolith of Mercury releases a fraction of its content to the exosphere. Some processes are identified up to now as leading to this ejection, e.g., photon-stimulated desorption. These processes are associated with different energies of ejection and behaviors in different regions of Mercury’s surface. Therefore, different types of population are born from the surface, depending on the processes. The MSASI measurements definitely can identify the release processes, how exospheric sodium is born from the regolith. MSASI/BepiColombo is the first and unique opportunity to study the formation, circulation, and maintenance of the surface-bounded exosphere.

Present Status of The KEK B-Factory Vacuum System

The KEK B-Factory (KEKB) is a two-ring electron-positron collider with asymmetric energies dedicated to proving the CP violation. The vacuum system has been working satisfactorily form the beginning of commissioning in December, 1998. The maximum stored beam currents are 1.3 A for the 8 GeV electron ring (High Energy Ring, HER), and 1.8 A for the 3.5 GeV positron ring (Low Energy Ring, LER). Most of the beam ducts are made of oxygen-free copper, owing to its ability to withstand an intense heat load and to effectively shield the radiation from high beam currents. The pumping scheme is a combination of Non-Evaporable Getter (NEG) pumps and auxiliary sputter ion pumps. An average pressure of about 1×10-7 Pa has been achieved for both rings at the maximum beam currents for both rings. The coefficient of photon-stimulated gas desorption has been decreasing steadily to less than 5×10-7 molecules photon-1 at an integrated linear photon density of about 1×1026 photons m-1. Although special care was taken to make the inside of the beam ducts as smooth as possible in order to avoid the excitation of higher order modes (HOM), the presence of high-current bunched beams has created several problems so far. The intense HOM has sometimes caused the heating of components near to some big HOM sources. Electron cloud around positron bunches led to an instability, which resulted in a vertical beam size blow-up in LER. A discussion about upgrading KEKB has just started aiming at a higher luminosity. The R & D of the vacuum components has also begun based on various experiences so far.

Low energy neutral atoms imaging of the Moon

Imaging of low-energy neutral atoms (LENAs) in the vicinity of the Moon can provide wide knowledge of the Moon from the viewpoint of plasma physics and planetary physics. At the surface of the Moon, neutral atoms are mainly generated by photon-stimulated desorption, micrometeorite vaporization and sputtering by solar wind protons. LENAs, the energetic neutral atoms with energy range of 10–500 eV, are mainly created by sputtering of solar wind particles. We have made quantitative estimates of sputtered LENAs from the Moon surface. The results indicate that LENAs can be detected by a realistic instrument and that the measurement will provide the global element maps of sputtered particles, which substantially reflect the surface composition, and the magnetic anomalies. We have also found that LENAs around dark regions, such as the permanent shadow inside craters in the pole region, can be imaged. This is because the solar wind ions can penetrate shaded regions due to their finite gyro-radius and the pressure gradient between the solar wind and the wake region. LENAs also extend our knowledge about the magnetic anomalies and associated mini-magnetosphere systems, which are the smallest magnetospheres as far as one knows. It is thought that no LENAs are generated from mini-magnetosphere regions because no solar wind may penetrate inside them. Imaging such void areas of LENAs will provide another map of lunar magnetic anomalies.

Desorption site-specificity and halogen minority sites on Si(1 1 1)

We identify the SiCl3 bonding geometry as the most desorption-active site in x-ray photon-stimulated desorption (XPSD) of positive chlorine ions from chlorinated Si(1 1 1) surfaces due to their much higher desorption cross-section in comparison to the on-top majority site. The novel combination of x-ray standing waves (XSW), XPSD and density functional theory (DFT) allows to quantitatively determine this trichloride adsorption geometry with high spatial resolution and to deduce the site-specific desorption cross-sections for Cl+ and Cl2+ ions, respectively. Additionally, these SiCl3 groups are shown to exhibit a preferential crystallographic orientation which is confirmed by both XSW and DFT. Moreover, the analoguous identification of desorption-active SiBr3 species for Br/Si(1 1 1) suggests a common physical origin of the site-specific desorption cross-sections.

Direct and indirect processes in photon-stimulated ion desorption from condensed formamide

A preliminary investigation of photon-stimulated ion desorption (PSID) from condensed deuterated formamide (HCOND 2) by using polarization-angle-dependent near-edge X-ray absorption fine structure (NEXAFS) spectroscopy combined with velocity-selected time-of-flight (TOF) mass spectrometry, is presented. It was found that the PSID yield of total D + ion is enhanced by the N 1s → σ*(N D) transition at both grazing and normal photon incidence angles and its enhanced yield shows no polarization dependence despite of direct PSID, which indicates the N D bonds are not aligned with the surface-oriented CNO molecular plane of HCOND 2. It was also found that the fastest velocity components of H + and D + ions monotonically decrease as the energy at the normal incidence angle. This finding suggests that X-ray-induced electron stimulated desorption (XESD) via secondary electrons resulting from valence photoelectrons; indirect PSID is a dominant process in the fastest components.

Mechanism of state-specific enhancement in photon-stimulated desorption as studied using a polarization-dependent technique

In the present study, we investigated the mechanisms of state-selective fragment-ion desorption from condensed chlorobenzene following C 1s, Cl 2s, and Cl 2p core-level excitations by measuring the polarization dependences of NEXAFS (near-edge X-ray absorption fine structure) spectra recorded with desorbed ion yields and total electron yields (TEY). TEY-based NEXAFS shows no significant polarization dependence at any edges. In contrast, ion-based NEXAFS demonstrates a variety of marked polarization dependences. Cl 2p → 3d π* excitation induces a significant enhancement of Cl + desorption yield at normal incidence (polarization ∥ surface), while Cl 2s → σ*(C–Cl) excitation stimulates a substantial enhancement of Cl + desorption at grazing incidence (polarization ⊥ surface). C 1s → σ*(C–Cl) enhances D + desorption at grazing incidence, while C 1s → π*(C C) suppresses D + desorption at all angles. All polarization dependences consistently reveal that excited molecules with upward-pointing bonds at top-most surfaces lead to efficient fragment desorption. This orientation effect is understood in terms of competing processes between the ultra-fast dissociation and charge-neutralization relaxation taking place during core-excited states. We demonstrate that the polarization-dependent ion-NEXAFS technique can distinguish direct state-specific fragmentation from indirect desorption caused by the collision of secondary electrons.

Photodesorption of ionized water clusters from water physisorbed on rare gas solids

The photon-stimulated desorption of (H 2O) n H + from water physisorbed on a rare gas solid (Ne, Ar, Kr, and Xe) has been investigated. From the measurements of the desorption yield as a function of the incident photon energy, the (H 2O) n H + desorption is effectively and indirectly induced by the multiple-excitation and -ionization of rare gas substrates. The direct excitation of the water molecule does not induce noticeable desorption of (H 2O) n H +.

Method and setup for photodesorption measurements for a nonevaporable-getter-coated vacuum chamber

This article describes a method for measurement of the photodesorption yield and sticking probability for a vacuum chamber coated with nonevaporable getter (NEG). This method is based on a three-gauge method of measurement which was developed and used on a specially designed and assembled setup for the photodesorption yield measurements of test chambers. It has been modified for photodesorption measurements of a vacuum chamber with sorbing walls. Although a short description of the installation and the results of the photodesorption measurements with the NEG-coated vacuum chamber have been published [V. V. Anashin, I. R. Collins, R. V. Dostovalov, N. V. Fedorov, A. A. Krasnov, O. B. Malyshev, and V. L. Ruzinov, The 8th European Particle Accelerator Conference, Paris, France, 2002, p. 2550; Vacuum 75, 155 (2004)], the details of the method, the analysis, and the experimental setup are also described in this article. Special attention is paid to define the sensitivity limit of the method and the setup and to reduce electron- and photon-stimulated desorption in the measurement port.

Estimation of picked-up lunar ions for future compositional remote SIMS analyses of the lunar surface

Abstract In situ measurement of Moon-originating ions picked-up in orbit round the Moon is expected to provide valuable information regarding the thin lunar atmosphere and surface. Secondary ions sputtered by the solar wind ions reflect the surface abundance. Global composition mapping of the lunar surface may be thus achieved by measuring the sputtered ions as one would perform laboratory SIMS.We studied the dynamics of picked-up lunar ions when the Moon was exposed to the solar wind. Our model’s source mechanism involved photoionization of the lunar exospheric atoms, photon-stimulated ion desorption, and ion sputtering. We propose that an intense flux of picked-up lunar ions (104 /cm2 sec) exists at an altitude of 100 km, for nearly a quarter of the orbit. The ion flux originating from the lunar surface is mono-directional and mono-energetic, and is distinguishable from that of lunar atmospheric origin whose energy spectra correspond to their spatial distribution. Our calculation suggested that ion measurements in orbit round the Moon enable remote SIMS analyses.

Search for a local effect in multiatom resonant core excitation in a surface species: Photoemission and photon-stimulated desorption fromN2on Ni(111)

We have investigated photoabsorption, N $1s$ photoelectron emission, and photon-stimulated desorption (PSD) of ${\mathrm{N}}^{+}$ ions, from ${\mathrm{N}}_{2}$ molecules perpendicularly chemisorbed on Ni(111) surfaces, in the energy range of the Ni $2{p}_{3∕2,1∕2}$ excitations. For this system, N $1s$ photoemission monitors single-core-hole production, whereas PSD of ${\mathrm{N}}^{+}$ is mainly due to excitation of multiply excited N $1s$ core-hole states. The amplitude variations of these two signals and the kinetic energy distributions (KED's) of the ${\mathrm{N}}^{+}$ ions were recorded as functions of the photon energy. In addition, we measured the amplitude variations of PE and PSD as a function of the photon incidence angle, which was varied from grazing (7\ifmmode^\circ\else\textdegree\fi{} with respect to the surface) to steeper angles (43\ifmmode^\circ\else\textdegree\fi{} and 50\ifmmode^\circ\else\textdegree\fi{} with respect to the surface). For grazing incidence, strong variations of both the photoelectron and the ${\mathrm{N}}^{+}$ signals with photon energy and angle of incidence were found in the Ni $2p$ region which are compatible with x-ray optical (dielectric) effects, one manifestation of multiatom resonant photoemission. The ${\mathrm{N}}^{+}$ KED's, which are known to depend strongly on the nature of the electronic excitation responsible, did not change across the Ni $2{p}_{3∕2}$ threshold, which excludes any type of state selectivity in the interatomic core-coupling effects observed. For N $1s$ photoemission, a first analysis of our data suggests a variation of the N $1s$ signal at the Ni $2p$ edges also for steeper angles of light incidence, of comparable magnitude to that at grazing incidence. However, more careful x-ray photoelectron spectroscopy experiments and the investigation of electronically stimulated desorption of neutral ${\mathrm{N}}_{2}$ molecules and N atoms reveal that these effects are due to a strong increase of beam damage when passing the Ni $2p$ edge; these effects could be reduced by rapidly scanning the sample under the beam. We thus conclude that for high angles of incidence most of the Ni $2p$-related changes in our N $1s$ photoemission signal are due to beam damage.