波长对Ag/TiO2催化剂上二氧化碳光催化还原的影响

Photocatalytic reduction of CO2 by water was performed in the presence of a Ag/TiO2 catalyst under illumination by lamps with different wavelengths(254,365,and 400 nm).The yields of the main products(methane and methanol)were higher with the 254 nm lamp than with the 365 lamp while no products were observed with the 400 nm lamp.This was because the electron-hole generation rate increased with increasing energy of irradiation(decreasing wavelength)and there were higher densities of electron states at higher energies in TiO2. The increased efficiency of electron-hole generation with a shorter wavelength irradiation increased the efficiency of the catalyst.The energy of the electrons excited by visible light(400 nm)was too low for CO2 photocatalytic reduction.     

Collective structures and smooth band termination in109Sn

Six rotational bands up to energies E _x =24.7 MeV and spinsj ^π=(79/2^?) have been identified in¹⁰⁹Sn using the GAMMASPHEREγ-detector array. Four of the bands show smoothly decreasing dynamic moments of inertia at rotational frequencies?ω>0.6 MeV. The bands arise at medium spins from a coupling of a valence d_5/2, g_7/2 or h_11/2 neutron to the deformed 2p2h proton excitation of the Z=50 core¹⁰⁸Sn. At very high?ω these bands show the typical behaviour of smoothly terminating bands, i.e. a gradual alignment of the angular momenta of the valence particles and holes corresponding to a transition from high collectivity to noncollective states.     

Spectroscopy of198,199Po

Excited states in^198,199Po have been studied by in-beamγ-ray spectroscopy. These nuclei were produced in the 4n and 5n reaction channels for 115 MeV²⁰Ne on¹⁸³W-targets. Multipolarities and mixing ratios ofγ-transitions were determined from DCO-ratios, leading to spin/parity assignments. In¹⁹⁸Po,γ-cascades have been observed above several excited levels that are similar to the vibration-like structure built on the ground state. In¹⁹⁹Po, the coupling of the oddi13/2 neutron seems to favor the spherical shape of the even core; no levels resembling the intruder states of the even nuclei are found. A semi-quantitative evaluation of the cross-sections for nuclei produced in fission and multi-particle transfer is presented.     

Dipole cascades in194Pb

Excited states in¹⁹⁴Pb, populated in the¹⁵⁸Gd(⁴⁰Ar,4n) reaction, were investigated using the OSIRIS γ-ray spectrometer array. The previously known level scheme is revised and substantially extended. Four cascades of dipole transitions are discussed.     

IDENTIFICATION OF MODAL PARAMETERS FROM MEASURED OUTPUT DATA USING VECTOR BACKWARD AUTOREGRESSIVE MODEL

In this paper, a modal identification system that is based on the vector backward autoregressive (VBAR) model has been developed for the identification of natural frequencies, damping ratios and mode shapes of structures from measured output data. The modal identification using forward autoregressive approach has some problems in discriminating the structure modes from spurious modes. On the contrary, the VBAR approach provides a determinate boundary for the separation of system modes from spurious modes, and an eigenvalue filter for the selection of physical modes is existent in the proposed method. For convenience of application, the backward state equation established from VBAR model is transformed into a forward state equation, which is termed as transformed VFAR model in this paper. In addition, the extraction of equivalent system matrix of state equation of motion for structures from the transformed VFAR model has been developed, and then the normal modes can be calculated from the identified equivalent system matrix. Two examples of modal identification are carried out to demonstrate the availability and effectiveness of the proposed backward approach: (1) Numerical modal identification for a three-degree-of-freedom dynamic system with noise level in 20% of r.m.s of measured output data; (2) experimental modal identification of a cantilever beam. Finally, to show the advantage of the proposed VBAR approach on the selection of physical modes, the modal identification by stochastic subspace method was performed. The results from both methods are compared.     

Stroboscopic observation of quadrupole hyperfine interactions

A stroboscopic technique for the observation of quadrupole hyperfine interactions of isomeric nuclear states has been successfully developed. The inherent precision and resolution of this technique have been demonstrated by measuring the quadrupole hyperfine frequency for ${}^{69}\text{Ge(}\text{9}\text{2}{}^{\mathrm{+}}{}_1\text{, τ = 4.0μ)}$ in Zn metal at several temperatures; ω₀ = [19.67 ± 0.06] × 10⁶s^?1 (at 623 ± 3 K).     

In-beamγ-ray spectroscopy of the neutron deficient100Ag

The neutron deficient nucleus¹⁰⁰Ag, three proton holes below and three neutron particles above the N=Z=50 shell closure at¹⁰⁰Sn, has been identified and studied by in-beam spectroscopy. The reactions⁴⁶Ti(⁵⁸Ni,3pn) at 231 MeV and⁶⁴Zn(⁴⁰Ca,3pn) at 167 MeV of the respective⁵⁸Ni and⁴⁰Ca beams were used, and states up to 8.7 MeV excitation energy and spin I?20 were found in two mainγ-ray cascades forming band-like structures of even and odd parity. Large scale shell model calculations suggest predominantπg ₉ ^2/?3 ν(d_5/2,g_7/2)³ andπg ₉ ^2/?3 ν(d_5/2,g_7/2)²h_11/2 structures with maximum spins I ^π = 19⁺ and I ^π =22^?, respectively, for the two level sequences. The influence ofπp_1/2 vs.νh_11/2 excitations is discussed for low lying odd-parity levels.     

Quadrupole and octupole collectivity in light Po isotopes

The level structure of¹⁹⁶Po has been studied using a¹⁶⁰Dy(⁴⁰Ar, 4n) reaction and a recoil-catcher technique to reduce fission. The results showed a sharp drop off in the first (2⁺) and (4⁺) energies relative to systematics implying an abrupt increase in the quadrupole collectivity at N=112. In addition, second (2⁺) and(4⁺) states were identified at 859 and 1388 keV, respectively, suggesting the discovery of a 4p2h deformed band in Po isotopes which is related to known 2p2h proton bands in several Pb isotopes. A prompt¹⁸³W(²⁰Ne, 5n@#@) experiment located similar second 2⁺ and 4⁺ states at 1039 and 1483 keV in¹⁹⁸Po providing corroboration and extended information on the properties of the new Po deformed bands. A measured halflife of 850 (90) ns for the 2491 keV (11^?) state in¹⁹⁶Po implied collective E3 contributions to the extractedB (@#@ E3; 11^?→8⁺)=27(5) W.u.     

The decay of theI π=8+ isomer in100Cd-neutron particle and proton hole states

The γ-decay and half life of the t_1/2=60(3) ns I^π=8⁺ isomer in¹⁰⁰Cd have been studied with a recoil catcher setup inside the multidetector π-array OSIRIS. Evaporation neutrons and charged particles from the reaction⁵⁸Ni+⁴⁶Ti were measured in coincidence with delayed γ-rays. Six new γ-ray transitions with intensities of 1–10% of the main γ-ray cascade were found, two new states established and firm spin-parity assignments were made to all states below the isomer. The new states were identified as the 4⁺ and 6⁺ members of the proton πg_9/2 ^?2 multiplet.