Characterization of photovoltaic cells using the photothermal deflection spectroscopy

The equilibrium segregation coefficientK ₀ of the following impurities has been measured in high-purity tellurium: Ag, Al, As, Cr, Cu, Fe, In, Mn, Ni, Pb, Pd, Ti, V, and their diffusion coefficient in liquid tellurium determined at 550 °C.     

双层材料光热偏转光谱的定量研究

从三线传热方程出发,给出了双层材料的光热偏转光谱的理论模型,讨论了光热偏转信号的特征及其在扫描成象应用中的意义.     

An investigation of the photothermal deflection spectroscopy technique for temperature measurements in a flame

The technique of photothermal deflection spectroscopy (PTDS) is investigated for temperature measurements in a flame. The spatial distribution of temperature is measured in two different types of burners operating with methane and oxygen, and methane and air. The spatial distributions of the temperature are in qualitative agreement with our expectations. At two points, the temperatures measured by PTDS have been compared with those measured by Boltzmann distributions. The measurements agree within their uncertainties. All the effects that affect the reliability of this technique are investigated and discussed. Finally, the pros and cons of the PTDS technique for temperature measurement are discussed. Received: 31 January 2002 / Published online: 8 August 2002     

Structural determination of a short-lived excited iron(II) complex by picosecond x-ray absorption spectroscopy

Structural changes of the iron(II)-tris-bipyridine ([Fe(II)(bpy)(3)](2+)) complex induced by ultrashort pulse excitation and population of its short-lived (< or =0.6 ns) quintet high spin state have been detected by picosecond x-ray absorption spectroscopy. The structural relaxation from the high spin to the low spin state was followed over the entire lifetime of the excited state. A combined analysis of the x-ray-absorption near-edge structure and extended x-ray-absorption fine structure spectroscopy features delivers an Fe-N bond elongation of 0.2 A in the quintet state compared to the singlet ground state.     

Theory of two-photon photothermal deflection spectroscopy in stationary and flowing media for arbitrary optical pulse length

A general theory of pulsed two-photon photothermal deflection spectroscopy (PTDS) is presented. We find that there are significant enough differences in the amplitude and temporal evolution of PTDS signals between the results of the single- and two-photon theories that if one tries to interpret two-photon data with single-photon theory, the extracted values may be considerably in error. Our theory is sufficiently general that it incorporates both stationary and flowing media and considers optical pulses of arbitrary length. Moreover, the temporal profile of the optical pulse is explicitly taken into account. The two-photon absorption coefficient is explicitly expressed in terms of oscillator strengths and Clebsch–Gordan coefficients, and the Doppler width for both co-propagating and counter-propagating beams is taken into account. Although the theory is primarily developed for atomic and molecular vapors, it can easily be adapted for condensed matter by expressing the absorption coefficient in terms of the properties of the liquid or solid under investigation. PACS 82.80.Kq; 42.62.Fi; 39.30.+w     

Application of the diffraction theory for photothermal deflection to measurements of thermophysical and mass-diffusion properties of gases

The application of recently developed diffraction theory for cw transverse photothermal deflection spectroscopy (normal deflection only) to the measurements of thermophysical and mass-diffusion properties of gases is presented. Compared with the traditional ray-optics theory, the diffraction theory has one more term in the phase signal. This term quantitatively exhibits the probe-beam size effect on the phase signal. Experimental results demonstrated that even if the ratio of the probe-beam radius to the thermal diffusion length of a deflecting medium was as low as about 0.22, the probe-beam size effect could not be ignored when measuring the distance between the probe beam and a solid sample using the phase signal. With the measured distance, the thermal diffusivity α_g and the temperature coefficient of the refractive index dn/dT of pure gases (O₂, N₂, and CO₂) and binary gas mixtures (CO₂-O₂ and CO₂-O₂) were precisely measured, resulting in good agreement with literature values. Furthermore the measured dn/dT values of the pure gases had one more significant figure than the literature ones. The concentration dependences of α_g and dn/dT were employed for the determination of mass-diffusion coefficients of CO₂-O₂ and CO₂-N₂, and the results were consistent with literature values.     

Effect of He+ and H+ ion irradiation on polystyrene films probed by NIR photothermal deflection spectroscopy

+ and H⁺ ions. Photothermal deflection spectroscopy (PDS) technique was used to record the absorption spectrum in the wavelength range 1.20 μm to 2.0 μm. The evolution of the various overtone and combination bands occurring in this range has been related to the changes taking place in the polystyrene structure. Received: 1 September 1998 / Accepted: 20 November 1998 / Published online: 24 February 1999     

Modeling for thermal conductivity measurements of thin films using photothermal deflection with obliquely crossed configuration

Received: 21 December 1996     

A simple theoretical extension to the analysis of photothermal deflection signal for low thermal diffusivity evaluation

A modified amplitude method to analyze the photothermal probe beam deflection signal for the determination of low thermal diffusivity values of materials is proposed. This simple theoretical model, which is an extension of the amplitude method proposed by Quelin et al., takes into account the dependence of the photothermal signal on the height of the probe beam above the sample surface which affects mirage measurements when the thermal diffusivity of the coupling medium is greater than that of the sample. The present work is similar to the modification to the phase method proposed by Bertolotti et al. for determination of low thermal diffusivity. The method can be applied irrespective of whether the sample is optically transparent or optically opaque and is independent of thickness.     

Bar-shaped nanoparticles of iron(II) hydroxide

Formation of elongated nanoparticles was observed when was precipitated from solutions containing excess of Fe²⁺. The average diameter of the particles was 23 nm; the length to diameter ratio was up to 14. This shape was an unexpected phenomenon because bar- or needle-like nanoparticles have been earlier reported only for Fe(III)-based materials. Chemical analysis revealed Fe(OH)₂ nature of the obtained particles. In addition, this conclusion was verified with a new simple method for quantitative evaluation of the particle morphology. Application of this method to the mixed samples allowed to distinguish between the two different compounds and to attribute different morphologies to Fe(OH)₂ or Results indicate that bars are frequent shapes of nano-sized iron oxides/hydroxides.     

Evaluation of the possibility of using the laser-induced thermocapillary effect for photothermal spectroscopy

A new approach to the photothermal spectroscopy of solids and liquids is proposed on the basis of the thermocapillary effect, which arises when a laser beam excites a layer of liquid several hundreds of millimeters thick lying on a solid surface. The method uses the measurement of the diameter of a thermocapillary response or the counting of the number of fringes of equal thickness observed in the light reflected from a thermocapillary depression. The detectability threshold and the resolution of the method correspond to absorbed optical powers of, respectively, 500 and 100 μW in the first case and 500 and 10 μW in the second case.     

Chemical modification of silica gel with synthesized new Schiff base derivatives and sorption studies of cobalt (II) and nickel (II)

In this study, three Schiff base ligands and their complexes were synthesized and characterized by infrared spectroscopy (IR), thermogravimetric analyses (TGA), nuclear magnetic resonance (NMR), elemental analysis and magnetic susceptibility apparatuses. Silica gel was respectively modified with Schiff base derivatives, (E)-2-[(2-chloroethylimino)methyl]phenol, (E)-4-[(2-chloroethylimino)methyl]phenol and N,N′-[1,4-phenilendi(E)methylidene]bis(2-chloroethanamine), after silanization of silica gel by (3-aminopropyl)trimethoxysilane (APTS) by using a suitable method. Characterization of the surface modification was also performed with IR, TGA and elemental analysis. The immobilized surfaces were used for Co(II) and Ni(II) sorption from aqueous solutions and values of sorption were detected by atomic absorption spectrometer (AAS).     

XAFS研究不同pH下土壤对Pb的吸附

利用X射线吸收精细结构光谱(XAFS)研究了不同初始pH条件下土壤吸附Pb(Ⅱ)的微观结构及吸附机理。表明土壤对Pb(Ⅱ)的吸附以形成Pb4(OH)44+的内圈吸附作用为主,其次为外圈吸附。同时,在吸附Pb(Ⅱ)过程中,Pb(Ⅱ)通过置换作用取代土壤中碳酸钙Ca(Ⅱ)的位置,形成含Pb碳酸钙(PbCaCO3)沉淀。土壤对Pb的吸附随初始pH(6.0~8.5)的增大,第一配位层(Pb—O)半径减小(0.172 7~0.166 6nm),内圈吸附比重加大,表明土壤对Pb(Ⅱ)的吸附机制受初始pH的影响。     

壳聚糖与不同金属锌盐配位的红外光谱研究

用壳聚糖和硫酸锌合成了一系列不同配比的配合物。通过对这些配合物红外光谱的分析和比较,考察了主要吸收峰随不同配比的变化规律,照发了它们的主要红外吸收峰,研究还表明,不同锌盐与壳聚糖形成的配合物有不同的配位环境。     

The sensitivity of thermal-lens and phase-shift (interferometric) techniques in photothermal spectroscopy: A comparative study

The thermal-lens and phase-shift (interferometric) techniques of photothermal spectroscopy are studied theoretically for the coaxial and mutually orthogonal propagations of probing and pumping beams. Respective expressions for the amplitude of detected signals are derived for the case of the volume absorption of pumping radiation. The sensitivities of the two techniques are numerically analyzed for different parameter values. It is demonstrated that the phase technique offers higher sensitivity especially if the size of the region with a perturbed temperature field is much larger than the probing beam radius.     

非分离状态下FI-KR-FAAS测定铁的价态

建立了流动注射(FI)编结反应器(KR)在线预富集与火焰原子吸收光谱(FAAS)联用非分离状态下测定铁的价态的新方法。进样流速6.0 mL.min-1;进样时间60s,测定0.04 mg.L-1的Fe(Ⅲ)和Fe(Ⅱ),Fe(Ⅲ)和Fe(Ⅱ)的浓集系数(EF)分别为41和9;检出限分别为2.5和14.3μg.L-1;相对标准偏差(RSD,n=11)分别为2.3%和3.1%。以0.1‰φ的三乙醇胺为掩蔽剂,Fe(Ⅲ)和Fe(Ⅱ)在水样中的回收率分别为97%～101%和96%～100%。     

Probe beam size effect on the measurement of the distance between the probe beam and the sample in photothermal deflection

A distance-scan method to determine the distance between the probe beam and sample, which is not easily measured exactly, in photothermal deflection (PD) was reported, with which the distance and thermal diffusivity of the deflecting medium can be simultaneously measured. Probe beam size effect (PBSE) on PD phase signal was quantitatively analyzed to clearly show its physical meaning. The measured distance was experimentally verified as correct and reliable, and the measured thermal diffusivities of N2 and CO2 are in good agreement with the literature values. They could not be precisely measured by phase signal without considering the PBSE.     

光热偏转光谱检测水中氯离子含量

本文应用光热偏转光谱（ＰＤＳ）检测水中微量元素氟离子的含量。它克服 常规光度方法测量溶液浓度中存在的二个干扰因素的影响，提高了检测灵敏度。讨论了ＰＤＳ信号随调制频率，泵浦光功率、探测光功率的变化，优化了测量装置的参数选择。     

The effects of the nature of the coupling gas and its pressure on infrared photothermal beam deflection spectra of solids

An entire aspirin tablet was confined in a pressure cell and infrared spectra were recorded with a Fourier transform beam deflection spectrometer using different coupling gases. The intensity S of spectra at 1 atm increased linearly in the order He < Ne < H₂ < N₂ ∼ Ar < CO₂ < CH₄, with increasing refractive index, n, except CO₂. As the pressure P was increased to 7 atm, S and S/noise increased ∼ 1.5-fold, but with H₂, the increases were ∼4-fold. The data indicate that the thermal conductivity k and dn/dP rather than dn/dP of the gases are the main causes of increases in S. The values for CO₂ were anomalously low, suggested to be caused by physical adsorption of CO₂ by the sample. Relatively large samples can be examined, and worthwhile S/noise enhancement can be obtained with pressure cells.