PLE spectra analysis of the sub-structure in the absorption spectra of CdSeS quantum dots

The semiconductor CdSeS quantum dots （QDs） embedded in glass are analysed by means of absorption spectra, photoluminescence （PL） spectra and photoluminescence excitation （PLE） spectra. The peaks of absorption spectra shift to lower energies with the size of QD increasing, which obviously shows a quantum-size effect. Using the PLE spectra, the physical origin of the lowest absorption peak is analysed. In PLE spectra, the lowest absorption peak can be deconvoluted into two peaks that stem from the transitions of 1S3/2-1Se and 2S3/2-1Se respectively. The measured energy difference between the two peaks is found to decrease with the size of QD increasing, which agrees well with the theoretical calculation for the two transitions. The luminescence peak of defect states is also analysed by PLE spectra. Two transitions are present in the PLE, which indicates that the transitions of 1S3/2 1Se and 2S3/2 1Se are responsible for the defect states luminescence.     

A new cell for X-ray absorption spectroscopy study under high pressure

X-ray absorption fine structure （XAFS） spectroscopy is a powerful technique for the investigation of the local environment around selected atoms in condensed matter. XAFS under pressure is an important method for the synchrotron source. We design a cell for a high pressure XAFS experiment. Sintered boron carbide is used as the anvils of this high pressure cell in order to obtain a full XAFS spectrum free from diffraction peaks. In addition, a hydraulic pump was adopted to make in-suit pressure modulation. High quality XAFS spectra of ZrH2 under high pressure （up to 13 GPa） were obtained by this cell.     

Measurements of pressure induced self-broadening and frequency shift coefficients of methane R9 manifold of 2v_3 band

An external-cavity diode laser (ECDL) has been used to investigate pressure-induced self-broadening as well as frequency shift of 2v3 band R9 manifold of methane. A phase sensitivity detection technology has been employed to determine the pressure induced frequency shift coefficient, however, which is obtained by line shape analyses of the recorded absorption spectrum. F1 and F2 unresolved double lines near 6105.626 cm-1 were measured as an object because they are often used to the high sensitivity detection of trace methane. The results show that the self-broadening and pressure induced frequency shift coefficients are 0.0232±0.003 and 0.0055±　0.0007 MHz/Pa, respectively.     

Measurements of pressure induced self-broadening and frequency shift coefficients of methane R9 manifold of 2v3 band

An external-cavity diode laser (ECDL) has been used to investigate pressure-induced self-broadening as well as frequency shift of 2v3 band R9 manifold of methane. A phase sensitivity detection technology has been employed to determine the pressure induced frequency shift coefficient, however, which is obtained by line shape analyses of the recorded absorption spectrum. F1 and F2 unresolved double lines near 6105.626 cm-1 were measured as an object because they are often used to the high sensitivity detection of trace methane. The results show that the self-broadening and pressure induced frequency shift coefficients are 0.0232±0.003 and 0.0055±0.0007 MHz/Pa, respectively.     

Effect of Nickel Alloying Layer on Hydrogen Absorption Ability of Zr-A1 Getter Material

By using ion beam sputtering, an 85-A thick nickel layer was deposited on the Zr-A1 alloy (non-evaporablegetter) to improve the characteristic of the hydrogen absorption. The presputtering for 15rain to clean thesurface passivation layer and the vacuum heating treatment of the sample at 750℃ for 1 h for surface alloyingcan improve the ability of the gas absorption. The gas absorption experiments show fast absorption kinetics of thehydrogen pumping and good durability against contaminable gases. The Rutherford-back-scattering spectra andthe secondary ion mass spectroscopy demonstrate the formation of an alloy of Zr, A1, and Ni in the near-surfacearea after the thermal process. The elastic recoil detection analysis indicates that the sample holds the originalhigh capacity of hydrogen.     

High-Pressure Phase Transition in CTAB-Micellar Solutions： A Raman Spectroscopic Study

We use a diamond anvil cell for the first time to investigate the Raman spectra of an aqueous micellar solution of hexadecyltrimethylammonium bromide （CTAB） at pressures up to 3.85 GPa. The pressure-induced phase transition between the micellar and coagel phases is found to occur at 0.64 GPa and 60℃. This phase transition has a pressure hysteresis, and thus exhibits the first-order phase transition properties. Further experimental results show that although the structure of the coagel phase is similar to that of the CTAB crystal, the interchain distance is slightly larger in the coagel phase than that in the CTAB crystal.     

Study of hot bands in the B2Σ+u-X2Σ+g system of C-2 anion

Optical heterodyne magnetic rotation enhanced velocity modulation spectroscopy was employed to observe the visible absorption spectra of the B^2Σ^+_u-X^2Σ^+_g electronic transition of C^-_2. Four hot bands (0,1), (1,2), (2,3) and (3,4) have been observed and the band (3,4) is measured directly for the first time, so far as we know, by absorption. A rotational analysis was carried out to obtain molecular constants. With the Franck－Condon principle and the vibrational Boltzmann distribution, we have estimated the vibrational temperature of C^-_2 to be about 3000K.     

Pressure-induced isostructural phase transition in α-Ni(OH)_2 nanowires

High pressure structural phase transition of monoclinic paraotwayite type α-Ni(OH)_2 nanowires with a diameter of15 nm–20 nm and a length of several micrometers were studied by synchrotron x-ray diffraction(XRD) and Raman spectra.It is found that the α-Ni(OH)_2 nanowires experience an isostructural phase transition associated with the amorphization of the H-sublattice of hydroxide in the interlayer spaces of the two-dimensional crystal structure at 6.3 GPa–9.3 GPa. We suggest that the isostructural phase transition can be attributed to the amorphization of the H-sublattice. The bulk moduli for the low pressure phase and the high pressure phase are 41.2(4.2) GPa and 94.4(5.6) GPa, respectively. Both the pressure-induced isostructural phase transition and the amorphization of the H-sublattice in the α-Ni(OH)_2 nanowires are reversible upon decompression. Our results show that the foreign anions intercalated between the α-Ni(OH)_2 layers play important roles in their structural phase transition.     

Pressure-induced anomalous insulating behavior in frustrated iridate La_3Ir_3O_(11)

The geometrically frustrated iridate La_3Ir_3O_(11) with strong spin–orbit coupling and fractional valence was recently predicted to be a quantum spin liquid candidate at ambient conditions. Here, we systematically investigate the evolution of structural and electronic properties of La_3Ir_3O_(11) under high pressure. Electrical transport measurements reveal an abnormal insulating behavior rather than metallization above a critical pressure P_c ～ 38.7 GPa. Synchrotron x-ray diffraction(XRD)experiments indicate the stability of the pristine cubic KSbO_3-type structure up to 73.1 GPa. Nevertheless, when the pressure gradually increases across P_c, the bulk modulus gets enhanced and the pressure dependence of bond length d_(Ir-Ir) undergoes a slope change. Consistent with the XRD data, detailed analyses of Raman spectra reveal an abnormal redshift of Raman mode and a change of Raman intensity around P_c. Our results demonstrate that the pressure-induced insulating behavior in La_3Ir_3O_(11) can be assigned to the structural modification, such as the distortion of IrO_6 octahedra. These findings will shed light on the emergent abnormal insulating behavior in other 5 d iridates reported recently.     

Modeling the interaction of nitrate anions with ozone and atmospheric moisture

The molecular dynamics method is used to investigate the interaction between one–six nitrate anions and water clusters absorbing six ozone molecules. The infrared(IR) absorption and reflection spectra are reshaped significantly, and new peaks appear at Raman spectra due to the addition of ozone and nitrate anions to the disperse water system. After ozone and nitrate anions are captured, the average(in frequency) IR reflection coefficient of the water disperse system increased drastically and the absorption coefficient fell.