LM优化算法在消光法测粒技术中的应用

基于限定模式反演算法,由LM优化算法对消光法测量衰减光谱进行反演处理,获得颗粒粒径和分布。讨论了目标函数构造,不同的粒径分布函数,单双峰分布及优化初值对于反演结果的影响及重要性。表明该算法具有很好稳定性和精确度。

Structural Dynamics of Phenyl Azide in Light-Absorbing Excited States： Resonance Raman and Quantum Mechanical Calculation Study

The excited state structural dynamics of phenyl absorbing S2（A＇）, S3（A＇）, and S6（A＇） states were troseopy and complete active space self-consistent and the UV absorption bands were assigned on azide （PhN3） after excitation to the light studied using the resonance Raman specfield calculations. The vibrational spectra the basis of the Fourier transform （FT）- Raman, FT-infrared measurements, the density-functional theory computations and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohex- ane, acetonitrile, and methanol solvents were, respectively, obtained at 273.9, 252.7, 245.9, 228.7, 223.1, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PhN3. The results indicated that the structural dynamics in the S2 （A＇）, S3（A＇）, and S6（A＇） states were significantly different. The crossing points of the potential energy surfaces, S2S1（1） and S2S1（2）, were predicted to play a key role in the low-lying excited state decay dynamics, in accordance with Kasha＇s rule, and NT=N8 dissociation. Two decay channels initiated from the Franck-Condon region of the S2（A＇） state were predicted： the radiative S2,min→S0 radiative decay and the S2→S1 internal conversion through the crossing points S2S1 （1）/S2S1（2）.

Decay Dynamics of N, N-Dimethylthioacetamide in S3（ππ＊） State

The decay dynamics of N, N-dimethylthioacetamide after excitation to the S3（ππ＊） state was studied by using the resonance Raman spectroscopy and complete active space self- consistent field method calculations. The UV-absorption and vibrational spectra were as- signed. The A-band resonance Raman spectra were obtained in acetonitrile, methanol and water with the laser excitation wavelengths in resonance with the first intense absorption band to probe the Franck-Condon region structural dynamics. The CASSCF calculations were carried out to determine the excitation energies and optimized structures of the lower- lying singlet states and conical intersection point. The A-band structural dynamics and the corresponding decay mechanism were obtained by the analysis of the resonance Raman in- tensity pattern and the CASSCF calculated structural parameters. The major decay channel of S3,FC （ππ＊）→S3（ππ＊）/S1 （nπ＊）→S1（nπ＊） is proposed.

Optimizing the nickel boride layer thickness in a spectroelectrochemical ATR-FTIR thin-film flow cell applied in glycerol oxidation

The influence of the drop-casted nickel boride catalyst loading on glassy carbon electrodes was investigated in a spectroelectrochemical ATR-FTIR thin-film flow cell applied in alkaline glycerol electrooxidation.The continuously operated radial flow cell consisted of a borehole electrode positioned 50μm above an internal reflection element enabling operando FTIR spectroscopy.It is identified as a suitable tool for facile and reproducible screening of electrocatalysts under well-defined conditions,additionally providing access to the selectivities in complex reaction networks such as glycerol oxidation.The fast product identification by ATR-IR spectroscopy was validated by the more time-consuming quantitative HPLC analysis of the pumped electrolyte.High degrees of glycerol conversion were achieved under the applied laminar flow conditions using 0.1 M glycerol and 1 M KOH in water and a flow rate of 5μL min^(–1).Conversion and selectivity were found to depend on the catalyst loading,which determined the catalyst layer thickness and roughness.The highest loading of 210μg cm^(–2)resulted in 73%conversion and a higher formate selectivity of almost 80%,which is ascribed to longer residence times in rougher films favoring readsorption and C–C bond scission.The lowest loading of 13μg cm^(–2)was sufficient to reach 63%conversion,a lower formate selectivity of 60%,and,correspondingly,higher selectivities of C_(2)species such as glycolate amounting to 8%.Thus,only low catalyst loadings resulting in very thin films in the fewμm thickness range are suitable for reliable catalyst screening.

Electrochemical CO2 Reduction on Pd-Modified Cu Foil

Bimetallic catalysts can improve CO2 reduction efficiency via the combined properties of two metals.CuPd shows enhanced CO2 reduction activity compared to copper alone.Using differential electrochemical mass spectrometry(DEMS)and electrochemical infrared(IR)spectroscopy,volatile products and adsorbed intermediates were measured during CO2 and CO reduction on Cu and CuPd.The IR band corresponding to adsorbed CO appears 300 mV more positive on CuPd than that on Cu,indicating acceleration of CO2 reduction to CO.Electrochemical IR spectroscopy measurements in CO-saturated solutions reveal similar potentials for CO adsorption and CO3^2-desorption on CuPd and Cu,indicating that CO adsorption is controlled by desorption of CO3^2-.DEMS measurements carried out during CO reduction at both electrodes showed that the onset potential for reduction of CO to CH4 and CH3OH on CuPd is about 200 mV more positive than that on Cu.We attribute these improvements to interaction of Cu and Pd,which shifts the d-band center of the Cu sites.

Infrared spectroscopic study on chemical and phase equilibrium in triethylammonium acetate

Protic ionic liquid (PIL) triethylammonium acetate was prepared by mixing equimolar amounts of acetic acid and triethylamine, and then studied using the combination of the Attenuated Total Reflection Fourier Transform Infrared spectroscopy, in-situ infrared spectroscopy, pH, and conductivity titration measurements. It was found that the equimolar synthesized triethylammonium acetate was separated into two layers, which suggesting that there were both chemical and phase equilibrium in this solution. Molecular species could be directly observed in the IR spectra over the range of 1200-1800 cm-1 and also checked by 1H NMR. Based on analysis, the upper layer was rich in amine with little acid and PIL, and the down layer was rich in PIL with residual acetic acid and amine. And single PIL-rich layer could be separated into two layers again when the mole ratio of newly added triethyamine to the theoretical produced triethylammonium acetate reached 0.12.

Quantitative deconvolution of autocorrelations and cross correlations from two-dimensional lifetime decay maps in fluorescence lifetime correlation spectroscopy

Fluorescence correlation spectroscopy （FCS） is a widely used method for measuring molecular diffusion and chemical kinetics. However, when a mixture of fluorescent species is taken into account, the conven- tional FCS method has limitations in extracting autocorrelations for different species and cross correla- tions between different species. Recently developed fluorescence lifetime correlation spectroscopy （FLCS） based on time-tagged time-resolved （TITR） photon recording, which can record the global and micro arrival time for each individual photon, has been used to discriminate different species according to fluorescence lifetime. Here, based on two-dimensional lifetime decay maps constructed from TITR photon stream, we have developed a quantitative lifetime-deconvolution FCS model （LDFCS） to extract precise chemical rates for chemical conversions in multi-species systems. The key point of LDFCS model is separation of different species according to the global distribution of fluorescence lifetime and then deconvolution of autocorrelations and cross-correlations from the two-dimensional lifetime decay maps constructed bv the micro arrival times of photon pairs at each delay time.

Influence of ring-down cavity parameters on intensity transmission property in trace gas concentration measurement

In this paper, we describe the basic principles and system design of continuous wave cavity ring-down spectroscopy （CWCRDS）. We also particularly study the nature and the behavior of a novel method to detune a laser and apply it to a cavity ring-down spectroscopy experiment. Both simulations and experiments are completed on the relation between the transmission characteristic and different refiectivities, as well as scanning speed. Output electric field equation is deduced. It has been investigated that how photons are coupled to the cavity and how to accumulate the intensity and leak out of the cavity as a function of time. It is noted that both accumulation of intensity and decay times decrease, and the oscillation amplitude increases as the reflectivity increases. Relative intensity increases with decreasing scanning velocity. Additionally, the simulations show that a non-detuned cavity displays the transmitted signals which are highly dependent on the mirror reflectivity and piezoelectric translator （PZT） modulation speed. Simulations also display that the laser switching off is different from dettming.