Abstract: INTRODUCTION FUNDAMENTAL ASPECTS OF CORE LEVEL SPECTROSCOPIES Core holes Overview of core level spectroscopies Interaction of x-rays with matter Optical transition operators and x-ray absorption spectrum The interaction of electrons with matter X-ray sources Electron sources MANY-BODY CHARGE-TRANSFER EFFECTS IN XPS AND XAS Introduction Many-body charge-transfer effects in XPS General expressions of many-body effects General effects in XPS spectra Typical examples of XPS spectra Many-body charge-transfer effects in XAS Comparison of XPS and XAS CHARGE TRANSFER MULTIPLET THEORY Atomic multiplet theory Ligand field multiplet theory The charge transfer multiplet theory X-RAY PHOTOEMISSION SPECTROSCOPY Introduction Experimental aspects XPS of TM compounds XPS of RE compounds Resonant photoemission spectroscopy Hard XPS Resonant inverse photoemission spectroscopy Nonlocal screening effect in XPS Auger photoemission coincidence spectroscopy Spin polarization and magnetic dichroism in XPS X-RAY ABSORPTION SPECTROSCOPY Basics of XAS Experimental aspects The L2, 3 edges of 3d TM systems Other x-ray absorption spectra of the 3d TM systems X-ray absorption spectra of the 4d and 5d TM systems X-ray absorption spectra of the 4f RE and 5f actinide systems X-RAY MAGNETIC CIRCULAR DICHROISM Introduction XMCD effects in the L2, 3 edges of TM ions and compounds Sum rules XMCD effects in the K edges of transition metals XMCD effects in the M edges of rare earths XMCD effects in the L edges of rare earth systems Applications of XMCD RESONANT X-RAY EMISSION SPECTROSCOPY Introduction Rare earth compounds High Tc Cuprates and related materials Nickel and Cobalt compounds Iron and Manganese compounds Early transition metal compounds Electron spin states detected by RXES and NXES MCD in RXES of ferromagnetic systems APPENDICES Precise derivation of XPS formula Derivation of Eq. (88) in Chapter 3 Fundamental tensor theory Derivation of the orbital moment sum rule Theoretical test of the spin sum rule Calculations of XAS spectra with single electron excitation models REFERENCES INDEX

Abstract: The broadband, coherent nature of narrow-linewidth fiber frequency combs is exploited to measure the full complex spectrum of a molecular gas through multiheterodyne spectroscopy. We measure the absorption and phase shift experienced by each of 155 000 individual frequency-comb lines, spaced by 100 MHz and spanning from 1495 to 1620 nm, after passing through hydrogen cyanide gas. The measured phase spectrum agrees with the Kramers-Kronig transformation of the absorption spectrum. This technique can provide a full complex spectrum rapidly, over wide bandwidths, and with hertz-level accuracy.

Abstract: Theoretical descriptions of two-dimensional (2D) vibrational and electronic spectroscopy are presented By using a coupled multi-chromophore model, some examples of 2D spectroscopic studies of peptide solution structure determination and excitation transfer process in electronically coupled multi-chromophore system are discussed A few remarks on perspectives of this research area are given

Abstract: Spatially resolved electron energy loss spectroscopy experiments have given the electromagnetic eigenmodes of individual metallic nanoparticles. The electromagnetic local density of states has been measured with 10 nm spatial accuracy over the whole near-infrared/ultraviolet regime.

Abstract: Using a fifth-order aberration-corrected scanning transmission electron microscope, which provides a factor of 100 increase in signal over an uncorrected instrument, we demonstrated two-dimensional elemental and valence-sensitive imaging at atomic resolution by means of electron energy-loss spectroscopy, with acquisition times of well under a minute (for a 4096-pixel image). Applying this method to the study of a La(0.7)Sr(0.3)MnO3/SrTiO3 multilayer, we found an asymmetry between the chemical intermixing on the manganese-titanium and lanthanum-strontium sublattices. The measured changes in the titanium bonding as the local environment changed allowed us to distinguish chemical interdiffusion from imaging artifacts.

Abstract: A facile method for the synthesis of size- and shape-controlled CuInS2 semiconductor nanocrystals was developed by thermolysis of a mixed solution of CuAc, In(Ac)3 (molar ratio of CuAc to In(Ac)3 = 1:1) and dodecanethiol in noncoordinating solvent 1-octadecene (ODE) at 240 °C. CuInS2 nanoparticles with size of 2 to ∼5 nm and nanorods with aspect ratio of 1 to ∼3 were obtained by adjusting the reaction parameters such as temperature and time. The as-prepared nanoparticles were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy, selected area electron diffraction spectroscopy, inductively coupled plasma atomic emission spectroscopy, UV−vis absorption, and photoluminescence (PL) spectroscopy. The nanoparticle solutions exhibit tunable absorption and PL spectra with the absorption edge ranging from 550 to 750 nm and PL emission peaks from 600 to 750 nm, indicating a strong size-dependent quantum confinement effect. Optical measurements of the CuI...

Abstract: Plasmon spectroscopy of the thinnest possible membrane, a single layer of carbon atoms: graphene, has been carried out in conjunction with ab initio calculations of the low loss function. We observe pi and pi+sigma-surface plasmon modes in free-standing single sheets at 4.7 and 14.6 eV, which are substantially redshifted from their values in graphite. These modes are in very good agreement with the theoretical spectra, which find the pi- and pi+sigma in-plane modes of graphene at 4.8 and 14.5 eV. We also find that there is little loss caused by out-of-plane modes for energies less than about 10 eV.

Abstract: We present the first ground-based detection of sodium absorption in the transmission spectrum of an extrasolar planet. Absorption due to the atmosphere of the extrasolar planet HD 189733b is detected in both lines of the Na I doublet. High spectral resolution observations were taken of 11 transits with the High Resolution Spectrograph (HRS) on the 9.2 m Hobby-Eberly Telescope (HET). The Na I absorption in the transmission spectrum due to HD 189733b is (− 67.2 ± 20.7) × 10−5 deeper in the "narrow" spectral band that encompasses both lines relative to adjacent bands. The 1 σ error includes both random and systematic errors, and the detection is >3 σ. This amount of relative absorption in Na I for HD 189733b is ~3 times larger than that detected for HD 209458b by Charbonneau et al. (2002) and indicates that these two hot Jupiters may have significantly different atmospheric properties.

Abstract: Silver nanoparticles were prepared by chemical reduction method. Silver nitrate was taken as the metal precursor and hydrazine hydrate as a reducing agent. The formation of the silver nanoparticles was monitored using UV-Vis absorption spectroscopy. The UV-Vis spectroscopy revealed the formation of silver nanoparticles by exhibing the typical surface plasmon absorption maxima at 418-420 nm from the UV-Vis spectrum. Comparison of theoretical (Mie light scattering theory) and experimental results showed that diameter of silver nanoparticles in colloidal solution is about 60 nm. We have used energy-dispersive spectroscopy (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and, UV-Vis spectroscopy to characterize the nanoparticles obtained. The energy-dispersive spectroscopy (EDX) of the nanoparticles dispersion confirmed the presence of elemental silver signal no peaks of other impurity were detected. The average size and morphology of silver nanoparticles were determined by transmission electron microscopy (TEM). TEM photographs indicate that the nanopowders consist of well dispersed agglomerates of grains with a narrow size distribution (40 and 60 nm), whereas the radius of the individual particles are between 10 and 20 nm. The synthesized nanoparticles have been structurally characterized by X-ray diffraction and transmission high-energy electron diffraction (HEED). The peaks in the XRD pattern are in good agreement with the standard values of the face-centered-cubic form of metallic silver (ICCD-JCPDS card no. 4-0787) and no peaks of other impurity crystalline phases were detected. Additionally, the antibacterial activity of the nanoparticulas dispersion was measured by Kirby-Bauer method. The nanoparticles of silver showed high antimicrobial and bactericidal activity against gram positive bacteria such as Escherichia Coli, Pseudimonas aureginosa and staphylococcus aureus which is a highly methicillin resistant strain.

Abstract: The localized surface plasmon resonance (LSPR) of Al nanoparticles fabricated by nanosphere lithography (NSL) was examined by UV−vis extinction spectroscopy and electrodynamics theory Al triangular nanoparticle arrays can support LSP resonances that are tunable throughout the visible and into the UV portion of the spectrum Scanning electron microscope and atomic force microscope studies point to the presence of a thin native Al2O3 layer on the surface of the Al triangular nanoparticles The presence of the oxide layer, especially on the tips of the nanotriangles, results in a significant red shift in the LSPR λmax The refractive index (RI) sensitivity of the Al triangular nanoparticle arrays in bulk solvents was determined to be 0405 eV/RIU Theoretical results show that the oxide layer leads to a significant decrease in this RI sensitivity compared to unoxidized triangular nanoparticles of similar size and geometry A comparison of Al, Ag, Cu, and Au triangular nanoparticles for a similar shape and g

Abstract: Quantum cascade (QC) lasers are virtually ideal mid-infrared sources for trace gas monitoring. They can be fabricated to operate at any of a very wide range of wavelengths from ∼ 3 μm to ∼ 24 μm. Seizing the opportunity presented by mid-infrared QC lasers, several groups world-wide are actively applying them to trace gas sensing. Real world applications include environmental monitoring, industrial process control and biomedical diagnostics. In our laboratory we have explored the use of several methods for carrying out absorption spectroscopy with these sources, which include multipass absorption spectroscopy, cavity ring down spectroscopy (CRDS), integrated cavity output spectroscopy (ICOS), and quartz-enhanced photoacoustic spectroscopy (QEPAS).

Abstract: We present an experimental study of the infrared conductivity, transmission, and reflection of a gated bilayer graphene and their theoretical analysis within the Slonczewski-Weiss-McClure (SWMc) model. The infrared response is shown to be governed by the interplay of the interband and the intraband transitions among the four bands of the bilayer. The position of the main conductivity peak at the charge-neutrality point is determined by the interlayer tunneling frequency. The shift of this peak as a function of the gate voltage gives information about less known parameters of the SWMc model such as those responsible for the electron-hole and sublattice asymmetries. These parameter values are shown to be consistent with recent electronic structure calculations for the bilayer graphene and the SWMc parameters commonly used for the bulk graphite.

Abstract: Phase-sensitive sum-frequency spectroscopy provides correct characterization of vibrational resonances of water-vapor interfaces and allows better identification of interfacial water species contributing to different parts of the spectra. Iodine ions emerging at an interface create a surface field that tends to reorient the more loosely bonded water molecules below the topmost layer.

Abstract: Surface phases of TiO2 nanoparticles (30 ∼ 200 nm) were studied by UV Raman spectroscopy and FT-IR spectroscopy with CO and CO2 as probe molecules. UV Raman spectroscopy can differentiate the surface phase structure of TiO2 calcined at different temperatures. IR spectra of adsorbed CO and CO2 on TiO2 calcined at different temperatures are in good agreement with the results from UV Raman spectra. IR results evidently confirm that UV Raman spectroscopy is a surface-sensitive technique for TiO2. Both UV Raman and IR spectra indicate that the crystalline phase of TiO2 in the surface region is usually different from that in the bulk which is characterized by XRD. CO is weakly adsorbed on Ti4+ ions of anatase phase but is hardly adsorbed on those of rutile phase at room temperature. Adsorbed CO2 on anatase phase produces mainly bidentate carbonate, while on rutile phase produces mainly bicarbonate species. These results suggest that the surface Lewis acidity of anatase phase is stronger than that of rutile phas...

Abstract: Ligand exchange offers an effective way to modify the properties of the recently prepared quantum clusters of gold. To tune optical and photoluminescence properties of one of the most stable quantum clusters of gold, Au25SG18 (SG-glutathione thiolate), we functionalized it by the exchange of −SG with functionalized -SG and with an altogether different ligand, namely, 3-mercapto-2-butanol (MB). The products were characterized by various techniques such as optical absorption (UV−vis), Fourier-transform infrared (FT-IR), nuclear magnetic resonance (NMR), X-ray photoelectron (XPS), and luminescence spectroscopies, mass spectrometry, and thermogravimetry (TG). Analyses of the TG data helped to establish the molecular composition of the products. Ligand exchange reaction was monitored by NMR spectroscopy, and it was found that the exchange reaction follows a first order kinetics. The XPS study showed that after the exchange reaction there was no change in the chemical nature of the metal core and binding energy...

Abstract: Real-time spectroscopy provides invaluable information about the evolution of dynamical processes, especially non-repetitive phenomena. Unfortunately, the continuous acquisition of rapidly varying spectra represents an extremely difficult challenge. One method, wavelength–time mapping, chirps the spectrum so that it can be measured using a single-shot oscilloscope1,2,3,4. Here, we demonstrate a method that overcomes a fundamental problem that has previously plagued wavelength–time spectroscopy: fine spectral resolution requires large dispersion, which is accompanied by extreme optical loss. The present technique uses an optically amplified wavelength–time transformation to beat the dispersion-loss trade-off and facilitate high-resolution, broadband, real-time applications. We show that this distributed amplification process can even be pumped by broadband noise, generating a wide gain bandwidth using a single pump source. We apply these techniques to demonstrate real-time stimulated Raman spectroscopy. Amplified wavelength–time Raman spectroscopy creates new opportunities for the study of chemical and physical dynamics in real time.

Abstract: We demonstrate on-chip laser absorption spectroscopy using silicon microring resonators integrated with PDMS microfluidic channels. A 100 microm radius microring resonator with Q > 100,000 is used to enhance the interaction length between evanescent light and a cladding liquid. We measure absorption spectra of less than 2 nL of N-methylaniline from 1460 nm to 1610 nm with 1 nm resolution and effective free space path lengths up to 5 mm. This work can help realize a completely on-chip spectroscopy device for lab-on-a-chip applications.

Abstract: Surface-enhanced infrared absorption spectroscopy in the attenuated total reflection mode is used to examine the structure of water on a polycrystalline Pt electrode in H2SO4 and HClO4 as a function of applied potential. The electrode surface covered with CO is used as the reference in recording spectra, which enables us to obtain the absolute infrared spectrum of the interfacial water layer (monolayer or bilayer) in contact with the surface with negligible interference from the bulk water. The spectrum of the interfacial water is largely different from that of bulk water and changes around the potential of zero charge of the electrode. The spectral changes are ascribed to the potential-dependent reorientation of water molecules from a weakly hydrogen-bonded oxygen-up orientation at the negatively charged surface to a strongly hydrogen-bonded nearly flat orientation at the positively charged surface in agreement with theoretical simulations reported in the literature. Clear experimental evidence of the fo...

Abstract: Surface-enhanced resonance Raman spectroscopy (SERRS) is a powerful technique for obtaining vibrational spectra of fluorescent molecules on metal surfaces. Raman scattering is strongly enhanced by two mechanisms: 1) molecular resonance occurs when the probe laser lies within the molecular electronic absorption, 2) electromagnetic or chemical enhancement occurs due to interaction with the metal surface. The combination of these effects results in a 10–10-fold enhancement in scattering, enabling single-molecule SERRS spectroscopy. However, due to the lack of resonance Raman (RR) spectra of fluorophores used in SERRS, the enhancement contributions from resonance and surface effects are difficult to separate and quantify. Although Raman techniques such as picosecond RR spectroscopy using Kerr gating and coherent anti-Stokes Raman scattering (CARS) are capable of rejecting fluorescence, these techniques are not ideal. Kerr-gated RR yields poor collection efficiency, while CARS has more complex lineshapes resulting in spectra that are more difficult to analyze. In contrast, the recently developed femtosecond stimulated Raman spectroscopy (FSRS) enables us to acquire and quantify RR cross-sections even in the presence of strong fluorescence. Here we exploit this fluorescence rejection capability of FSRS to obtain a RR spectrum of the highly fluorescent dye rhodamine 6G (R6G) and quantify its resonance Raman scattering cross-sections. This result allows an estimate of the magnitude of surface and resonance enhancements in SERRS. Recent progress has advanced SERRS technology to the single-molecule detection limit. SERRS experiments performed at wavelengths close to the absorption maximum of R6G resulted in a Raman cross-section of ~10 14 cm molecule . Comparable or higher enhancements were reported for molecules adsorbed on colloidal silver or gold clusters in SERS experiments performed at near-infrared excitation: however, the anomalous enhancements may be due to the presence of colloidal clusters where the concentration of adsorbed molecules is higher. Therefore, SERRS experiments with excitation wavelengths close to the absorption maximum are the most direct way of achieving optimal sensitivity for single molecule detection. However, it is difficult to determine how much of the enhancement is due to field effects, because conventional resonance Raman intensities are difficult to measure directly on resonance. FSRS is a powerful new structural probe of chemical and biological systems in both steady-state and time-resolved studies. Following a femtosecond actinic pulse, the simultaneous interaction of a 800 nm narrow-bandwidth picosecond Raman pump and a broadband femtosecond continuum Raman probe leads to the production of sharp vibrational gain features on top of the dispersed probe envelope. These gain features constitute the broadband stimulated Raman spectrum (SRS). FSRS has been successfully used to study a variety of chemical reaction dynamics—such as the first step in vision— with unprecedented information content. We have also extended FSRS into the visible range where many chemical and biological systems of interest absorb. Since SRS provides the same information as spontaneous Raman spectroscopy and is insensitive to fluorescence, it should also be useful in determining the RR cross-sections of R6G. Herein, we present the measurement and quantitative analysis of the RR spectra of R6G resonant with the absorption maximum using SRS. Additionally, we have performed Raman intensity analysis to predict how the cross-sections will vary with excitation wavelength. Figure 1 presents the SRS spectrum of R6G obtained with 532 nm excitation after subtraction of the broad background. The frequencies are in good agreement with earlier RR results obtained with excitation at 457 nm and at 488 nm, while

Abstract: Measurements of thickness using electron energy loss spectroscopy (EELS) are revised. Absolute thickness values can be quickly and accurately determined with the Kramers-Kronig sum method. The EELS data analysis is even much easier with the log-ratio method, however, absolute calibration of this method requires knowledge of the mean free path of inelastic electron scattering lambda. The latter has been measured here in a wide range of solids and a scaling law lambda approximately rho(-0.3) versus mass density rho has been revealed. EELS measurements critically depend on the excitation and collection angles. This dependence has been studied experimentally and theoretically and an efficient model has been formulated.

Abstract: We report modulation transfer spectroscopy on the D2 transitions in 85Rb and 87Rb using a simple home-built electro-optic modulator (EOM). We show that both the gradient and amplitude of modulation transfer spectroscopy signals, for the 87Rb F = 2 → F' = 3 and the 85Rb F = 3 → F' = 4 transitions, can be significantly enhanced by expanding the beams, improving the signals for laser frequency stabilization. The signal gradient for these transitions is increased by a factor of 3 and the peak to peak amplitude was increased by a factor of 2. The modulation transfer signal for the 85Rb F = 2 → F' transitions is also presented to highlight how this technique can generate a single, clear line for laser frequency stabilization even in cases where there are a number of closely spaced hyperfine transitions.

Abstract: Recent progress in the development of room temperature, continuous wave, widely tunable, mode-hop-free mid-infrared external cavity quantum cascade laser (EC-QCL) spectroscopic sources is reported. A single mode tuning range of 155 cm-1 (∼ 8% of the center wavelength) with a maximum power of 11.1 mW and 182 cm-1 (∼ 15% of the center wavelength) with a maximum power of 50 mW was obtained for 5.3 and 8.4 μm EC-QCLs respectively. This technology is particularly suitable for high resolution spectroscopic applications, multi species trace-gas detection and spectroscopic measurements of broadband absorbers. Several examples of spectroscopic measurements performed using EC-QCL based spectrometers are demonstrated.

Abstract: Monodisperse ZnO:Eu nanocrystals were prepared by the codecomposition of metal acetylacetonate precursors in a mixture of oleylamine and 1-octadecene. They have been systematically characterized by means of X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, inductively coupled plasma atomic emission spectrometry, Raman spectroscopy, and photoluminescence spectroscopy. The as-obtained ZnO:Eu nanocrystals are mainly composed of nanopyramids and dot-shaped nanocrystals and have an average size in the range of 16−32 nm. The valence states of europium ions in the nanocrystals are determined as predominately +3. With increasing dopant concentration of Eu3+ ions, Eu2O3 species tend to segregate on the surfaces of nanocrystals. Under a typical band-edge excitation of ZnO (380 nm), a direct energy transfer from ZnO host to Eu3+ ions, together with a distinct quenching of broad defect emission of ZnO, was observed for the as-obtained doped nanocrystals.