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High-harmonic generation
Published in Guo-ping Zhang, Georg Lefkidis, Mitsuko Murakami, Wolfgang Hübner, Tomas F. George, Introduction to Ultrafast Phenomena from Femtosecond Magnetism to high-harmonic Generation, 2020
Guo-ping Zhang, Georg Lefkidis, Mitsuko Murakami, Wolfgang Hübner, Tomas F. George
To understand the origin of other high-order harmonics, a method, that is very popular in the resonant inelastic x-ray scattering (RIXS) [Zhang et al. (2002a)], is very handy. In RIXS, one sends in x-ray photons and collects emitted photons. A spectrometer can measure the emitted photon energy. If we increase the incident photon energy, the emitted photon energy may or may not change. If the emitted photon energy does not change with respect to the incident photon energy, then the associated transition must correspond to the intrinsic electron states. Figure 4.11(b) shows that the energies of the first and third harmonics scale linearly with the incident energy, but peak e does not. This shows that there is a fundamental difference among those harmonic peaks. Peaks like peak e originate from those intrinsic transitions that involve the energy states. Figure 4.11(c) shows that nearly all the peaks can be attributed to unique transitions.
Structural and Optical Properties of Zn1−xCuxO Thin Films
Published in Zhe Chuan Feng, Handbook of Zinc Oxide and Related Materials, 2012
Ram S. Katiyar, Kousik Samanta
The NEXAFS and resonant inelastic x-ray scattering (RIXS) techniques are the most powerful to identify the valence states of ions and to differentiate between the localized ions (substitution or interstitial) and metallic clusters in the complex materials system. The element-specific NEXAFS and RIXS spectroscopy is capable of probing the partial density of unoccupied and occupied states of constituent elements, respectively, and thus are powerful tools for understanding local electronic structure around target atoms.
Near-Infrared Phosphors with Persistent Luminescence over 1000 nm for Optical Imaging
Published in Ru-Shi Liu, Xiao-Jun Wang, Phosphor Handbook, 2022
Jian Xu, Michele Back, Setsuhisa Tanabe
Concerning the efforts on underlying the mechanism of PersL, the discovery of SrAl2O4:Eu2+–Dy3+ by Matsuzawa et al. also marked the beginning of a renewed search for it. Until then, relatively little research had been done on this subject. The proposed mechanism at that time was described by the hole trapping-detrapping model as follows: when the Eu2+ ion is excited by an incident photon, a hole escapes to VB, thereby leaving behind an Eu+ ion, while the liberated hole is then captured by the co-doping Dy3+ ion creating a Dy4+ ion [140, 177]. However, it seems to be quite improbable considering the required huge amount of energy to form Eu+ under ambient conditions. Instead, in the same year (1996), S. Tanabe proposed a new model [178], in which Eu3+ was created after leaving an electron to CB while the Dy3+ ion captured the escaped electron through CB to be Dy2+. Nowadays, it is well known as the electron trapping-detrapping model and has been widely used as one of the most acceptable mechanisms to explain PersL. This hypothesis was strongly supported by the existence of Eu3+ species under excitation through the XANES results [179], and the observation of the current rise by photocurrent excitation (PCE) measurements also confirmed the photoionization process of excited electrons from the Eu2+:5d state into CB at RT [180]. Although the reduction of Dy valence state from 3+ to 2+ serves as an open question for a long time, very recently, a dedicated resonant inelastic X-ray scattering (RIXS) study with the help of synchrotron radiation demonstrated by P.F. Smet et al. gave a strong evidence of valence state change from Dy3+ to Dy2+ in a similar strontium aluminate host (Sr4Al14O25) during charging process [181], which answered this long-standing question of the electron trapping-detrapping model. Below, two popular charge carrier trapping models of PersL, i.e., electron trapping-detrapping and hole trapping-detrapping, are introduced.
Positive temperature coefficient of the thermal conductivity above room temperature in a perovskite cobaltite
Published in Science and Technology of Advanced Materials, 2022
Atsunori Doi, Satoshi Shimano, Markus Kriener, Akiko Kikkawa, Yasujiro Taguchi, Yoshinori Tokura
Although extensive investigations have been conducted in recent decades, the nature of the spin-state in the intermediate temperature regime (100 K < T < 500 K) remains still controversial. The uniform IS-state phase with ordering of active eg orbital is proposed by ab-initio calculations, optical measurements, x-ray diffraction, and electron energy loss spectroscopy [12–17]. On the other hand, a spatially inhomogeneous spin-state model, i.e. spin-state disproportionation composed of LS and HS, is suggested as another possible model [18–24]. Recently, dynamical aspects of thermally excited spin-states have been investigated by infrared spectroscopy measurements, resonant inelastic x-ray scattering, and theoretical calculations [11,25,26]. Exotic phases induced by epitaxial strain [27–30] and ultra-high magnetic field [31,32] have also been discussed in LaCoO3.
Distinctive applications of synchrotron radiation based X-ray Raman scattering spectroscopy: a minireview
Published in Instrumentation Science & Technology, 2021
The unique characteristics of third-generation synchrotron light sources such as tunable energy from ultraviolet to hard X-rays, high brilliance over a broad energy range, low emittance, pulsed time structure, controlled polarization and high beam stability in terms of intensity and position[1] have enabled the development of various advanced experimental techniques.[2–4] X-ray Raman scattering (XRS) is a synchrotron radiation based non-resonant inelastic X-ray scattering (NRIXS) technique. In inelastic X-ray scattering (IXS), incoming photon transfers a portion of its energy and momentum to the system of interest and induces several excitations such as Compton scattering, core-electron excitations or phonon excitations[5–7] as presented in Figure 1.
Self-assembly and tiling of a prochiral hydrogen-bonded network: bi-isonicotinic acid on coinage metal surfaces
Published in Molecular Physics, 2023
Alexander Allen, Mohammad Abdur Rashid, Philipp Rahe, Samuel P. Jarvis, James N. O'Shea, Janette L. Dunn, Philip Moriarty
The molecule on which we focus in this paper, bi-isonicotinic acid (4,4'-COOH-2,2'-bpy, Figure 1(a)), is not only a prototypical prochiral species but a key component of the ruthenium dye known as ‘N3’ or Ru535 – in full, cis-bis(isothiocyanato) bis(2,2'-bipyridyl-4,4'-dicarboxylic acid) ruthenium(II) – that is in turn at the heart of many model dye-sensitised solar cell systems [7]. These include the highly influential Grätzel architecture [8]. The N3 ruthenium complex bonds to oxide surfaces such as TiO – the substrate used in the Grätzel cell (in a nanostructured form) – via the carboxyl groups of the bi-isonicotinic acid ligands. Charge transfer will therefore be strongly mediated by the adsorption, conformation, and intermolecular interactions of the tethered bi-isonicotinic acid groups. There has thus been a series of studies focussed on the adsorption of bi-isonicotinic acid on a variety of surfaces (with an unsurprising emphasis on TiO), and in bulk, or thin film, form [9–11]. In particular, one of the authors (JNOS) and co-workers have carried out extensive photoemission, X-ray absorption spectroscopy, and, more recently, resonant inelastic X-ray scattering (RIXS) measurements of not just bi-isonicotinic acid (sub)monolayers and thin films on metal and oxide substrates, but of the entire adsorbed N3 complex [12–14]. Although aggregates of N3 on Au(111) have been imaged using scanning tunnelling microscopy (STM) [15], scanning probe microscopy measurements of bi-isonicotinic acid assemblies have been lacking to date.