Soft X-Ray Absorption Spectra of Alkali Halides. I. KCl and NaCl

Sagawa, T.; Iguchi, Y.; Sasanuma, Michio; Nasu, Takao; Yamaguchi, S.; Fujiwara, S.; Nakamura, Masatoshi; Ejiri, Arisato; Masuoka, Toshio; Sasaki, Taizo; Oshio, Takanori

doi:10.1143/jpsj.21.2587

Cited by 66 publications

(8 citation statements)

References 18 publications

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“…In the case of LiCl the chlorine .Ln.m structure (2/> 6 shell) can be seen at 200 eV. Spectral details are similar to those previously reported by Iguchi et al 6 These high-energy transitions appear weaker than those at 60 eV when a is plotted. On the other hand, the transition probability W if is proportional to coa, and on this basis it can be seen that the 2/> 6 spectrum is actually stronger overall than the Is 2 spectrum, in agreement with the larger number of electrons involved.…”

supporting

confidence: 84%

Soft X-Ray Spectra of the Lithium Halides and Their Interpretation

et al. 1970

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The photoabsorption of LiF, LiCl, and LiBr has been investigated with high resolution at quantum energies from 60 to 230 eV using synchrotron radiation from an electron storage ring. It is found that the spectra can be understood largely in terms of transitions from the various core levels to the final-band density of states as obtained from recent band calculations. Features are found which may possibly be due to replication of the edge with the emission of one or more collective excitations. Substantial progress has recently been made toward a detailed understanding of the optical response of LiF, LiCl, and LiBr over a wide range of energies in the extreme ultraviolet. The lithium K shell provides especially suitable initial states because of large dipole matrix elements with the final band states and also the lack of strong resonances in the continuum beyond threshold. 1 Previous results on the lithium halides have been reported by Haensel, Kunz, and Sonntag in the spectral range 60-70 eV. 2 The present measurements extend some 150 eV higher in energy, and they provide values of absorption coefficient so that the importance of transitions from the various core states, for example, the Li + K, the Cl~ L n>m , the Br" M IVt v? and the Br"" M n>in can be assessed. Moreover, it has recently been possible to carry out a self-consistent Hartree-Fock energy-band calculation including the principal polarization or many-body corrections for LiCl 3 and also for LiBr. 4 This permits the comparison of theoretical and experimental optical spectra so as to determine the importance of core excitons and multiple excitations.The absorption coefficients were determined by observing the transmission of thin films of various thicknesses evaporated in situ onto thin Formvar substrates. Film thicknesses were determined by a quartz crystal monitor calibrated by the Tolansky technique. The synchrotron continuum from the 240-MeV electron storage ring at the University of Wisconsin Physical Science Laboratory was used as a light source. Radiation transmitted by the substrates (and by the substrates plus samples) was dispersed by a 2m grazing-incidence spectrometer with 10-/Lim entrance slits and a 576-line/mm grating. Digital recording of the photon counting rate as well as monitor and wavelength information was employed during scans of about 30 min each. When structure appeared it was possible to slow down the scanning rate so as to include many more points in the same wavelength interval. Scans were repeated and later combined during the computer analysis. The data reduction techniques, methods for filtering out stray light, etc., are described elsewhere. 5 Absolute absorption coefficients were determined to 30% accuracy and the wavelength resolution was 0.1 A. Measurements were made with the film at room temperature since little narrowing of the observed structure occurred upon cooling to 77°K. Figure 1 shows the experimental results for the three materials over a wide spectral range. The absorption coefficients a (cm"" 1 ) are plot...

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supporting

confidence: 84%

Soft X-Ray Spectra of the Lithium Halides and Their Interpretation

et al. 1970

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“…The EXAFS data of the MSL and bulk samples are nearly same (after excluding noise signals), indicating their common covalent bond lengths within the BiOCl layer. For the XANES results, the pre-edge P1 and P2 peaks, which represent the transitions from Cl 1 s orbital to unoccupied hybridized Bi 6 p and Cl 3 p orbitals 63 , show clear differences between these two cases. This originates from their distinct bonding/interaction among layers that have essential effect on the unoccupied conduction bands formed by hybridized Bi 6 p and Cl 3 p orbitals.…”

Section: Resultsmentioning

confidence: 95%

“…b , c Comparison of XANES (Cl K-edge) and EXAFS spectra collected on BiOCl bulk and BiOCl MSL samples, respectively. In ( b ) the pre-edge P1 and P2 peaks represent the transitions from Cl 1 s orbital to unoccupied hybridized Bi 6 p and Cl 3 p orbitals, and the P3 peak represents the Cl 1 s → Cl 4 p transition 63 . d The near-field amplitude image from s-SNOM measurement showing distribution of free carriers.…”

Section: Resultsmentioning

confidence: 99%

Bottom-up growth of homogeneous Moiré superlattices in bismuth oxychloride spiral nanosheets

et al. 2019

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Moiré superlattices (MSLs) are modulated structures produced from homogeneous or heterogeneous 2D layers stacked with a twist angle and/or lattice mismatch. Expanding the range of available materials, methods for fabricating MSL, and realization of unique emergent properties are key challenges. Here we report a facile bottom-up synthesis of homogeneous MSL based on a wide-gap 2D semiconductor, BiOCl, using a one-pot solvothermal approach with robust reproducibility. Unlike previous MSLs usually prepared by directly stacking two monolayers, our BiOCl MSLs are realized in a scalable, direct way through chemical growth of spiral-type nanosheets driven by screw-dislocations. We find emergent properties including large band gap reduction (∼0.6 eV), two-fold increase in carrier lifetime, and strongly enhanced photocatalytic activity. First-principles calculations reveal that such unusual properties can be ascribed to the locally enhanced inter-layer coupling associated with the Moiré potential modulation. Our results demonstrate the promise of MSL materials for chemical and physical functions.

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“…We do not find any remarkable steps of absorption ( k or e3) but only an absorption peak at this energy so that we are not sure that such a process takes place. In the sodium chlorides where such a process was first suggested [23] the situation is somewhat different since a significant step in the absorption coefficient has been found at about the expected energy when the Nat2p core excitations were studied experimentally [24]. Theoretical investigations on double excitations give contradictory results for the probability of such a process [25, 261.…”

Section: Discussionmentioning

confidence: 99%

Dielectric Properties of KCl, KBr, and KI Single Crystals in the Extreme Ultraviolet up to 35 eV

Blechschmidt¹,

Klucker²,

Skibowski³

1969

Physica Status Solidi (b)

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The reflectance of freshly cleaved single crystals of KCI, KBr, and K I has been measured for 15" angle of incidence a t room temperature for photon energies between 5 and 35 eV, using the continuous spectrum of synchrotron radiation. For photon energies from 12 t o 30eV the optical constants, the dielectric constant, and the energy loss function were determined by reflectance measurements with parallel polarized light a t several angles of incidence between 15' and 75". A prominent doublet near 20 eV is found for all potassium halides. It is assigned to excitonic transitions from the K+3p core level to the conduction band a t r a n d X . Energy differences between some critical points a t T and X are estimated

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Soft X-Ray Absorption Spectra of Alkali Halides. I. KCl and NaCl

Cited by 66 publications

References 18 publications

Soft X-Ray Spectra of the Lithium Halides and Their Interpretation

Soft X-Ray Spectra of the Lithium Halides and Their Interpretation

Bottom-up growth of homogeneous Moiré superlattices in bismuth oxychloride spiral nanosheets

Dielectric Properties of KCl, KBr, and KI Single Crystals in the Extreme Ultraviolet up to 35 eV

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