China
Africa
Explore chapters and articles related to this topic
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.
EOM-CC methods with approximate triple excitations applied to core excitation and ionisation energies
Published in Molecular Physics, 2020
The use of X-rays to investigate the structure and dynamics of molecules and materials is long established [1–4], but recent advances in X-ray sources, particularly free-electron lasers, have initiated a renaissance in X-ray absorption (NEXAFS, XPS) and emission/scattering (XES/RIXS) applications [5–9]. Computationally, a number of techniques are available to simulate X-ray spectra with varying levels of fidelity and computational cost [10,11], including DFT-based approaches such as time-dependent DFT (TD-DFT) [12–16], ΔDFT (ΔKS) [17–22], and transition-potential DFT (TP-DFT) [17,23,24], as well as algebraic diagrammatic construction (ADC) methods [25,26]. More recently, there has been an increased interest in applying advanced wavefunction-based electronic structure methods, in particular equation-of-motion coupled cluster (EOM-CC) theory [27–30] to the X-ray regime [31–45].
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.