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With simulation of absorption spectra in THz region based on quantum-chemical calculation, the THz absorption features of target materials can be assigned with theoretical normal vibration modes. This is necessary for deeply understanding the origin of THz absorption spectra. The reliabilities of simulation results mainly depend on the initial structures and theoretical methods used throughout the calculation. In our study, we utilized THz-TDS to obtain the THz absorption spectrum of solid-state L-glutamine. Then three quantum-chemical calculation schemes with different initial structures commonly used in previous studies were proposed to study the inter-molecular interactions' contribution to the THz absorption of glutamine, containing monomer structure, dimer structure and crystal unit cell structure. After structure optimization and vibration modes' calculation based on density functional theory, the calculation results were converted to absorption spectra by Lorentzian line shape function for visual comparison with experimental spectra. The result of dimmer structure is better than monomer structure in number of absorption features while worse than crystal unit cell structure in position of absorption peaks. With the most reliable simulation result from crystal unit cell calculation, we successfully assigned all three experimental absorption peaks of glutamine ranged from 0.3 to 2.6 THz with overall vibration modes. Our study reveals that the crystal unit cell should be used as initial structure during theoretical simulation of solid-state samples' THz absorption spectrum which comprehensively considers not only the intra-molecular interactions but also inter-molecular interactions.

Using THz-TDS to extract the absorption spectrum of a sample is an important branch of various THz applications. Basically, we believe that the THz radiation scatters from sample particles, leading to an obvious baseline increasing with frequencies in its absorption spectrum. The baseline will affect the measurement accuracy due to ambiguous height and pattern of the spectrum. The authors should try to remove the baseline, and eliminate the effects of scattering. In the present paper, we investigated the causes of baselines, reviewed some of scatter mitigating methods and summarized some of research aspects in the future. In order to validate the correctness of these methods, we designed a series of experiments to compare the computational accuracy of molar concentration. The result indicated that the computational accuracy of molar concentration can be improved, which can be the basis of quantitative analysis in further researches. Finally, with comprehensive experimental results, we presented further research directions on THz absorption spectrum that is needed for the removal of scattering effects.

The present paper discusses the Lambert-Beer' s law application in the terahertz spectrum, studies the single amino acid tablet sample (glutamine) and two kinds of amino acids mixture tablet (threonine and cystine) under the condition of different concentrations. Absorbance and absorption coefficient was analyzed in the description of the terahertz optical properties of matter. By comparing absorption coefficient and absorbance value of the single component in the vicinity of 1. 72 THz, we verified the material under two kinds of absorption characterization of quantity of THz wave absorption along with the change in the concentration. Using the index of goodness of fit R , it studied the stand or fall of linear relationship between the terahertz absorption quantity of material and concentration under two kinds of representation. This paper analyzes the two components mixture under two kinds of absorption characterization of quantity of terahertz absorption in 0. 3-2. 6 THz. Using the similarity co- efficient and the estimate concentration error as evaluation index, it has been clear that the absorbance of additivity instead of the absorption coefficient should be used during the terahertz spectrum quantitative test, and the Lambert-Beer's law application in the terahertz wave band was further clarified.

Using THz-TDS to detect the THz temporal pulse and calculate the absorption spectrum of the sample is the main access to qualitative and quantitative analysis. The shape and the amplitude of the THz absorption spectra are not only related to the sample, but also closely related to the length of the chosen THz pulse in the calculation, which was discovered in our experiments. It is the main cause of this problem that the flaky sample reflects the THz wave many times, which will give rise to the Fabry-Perot effect. So the sample-probing temporal signal is divided into the intrinsic section with the sample's information directly, low SNR noise section, and unwanted Fabry-Perot reflections section with the overlapped information. Based on THz pulse generation mechanism and the relationship between the pulse amplitude and the attenuate process, a model of intercepting the intrinsic section in terahertz time-domain pulse was proposed and was proved reliable and stable by the results from experiments performed with amino acids: glutamine(Gln), histidine(His), and cystine(Cys).

Extracting absorption spectrum in THz band is one of the important aspects in THz applications. Sample's absorption coefficient has a complex nonlinear relationship with its thickness. However, as it is not convenient to measure the thickness directly, absorption spectrum is usually determined incorrectly. Based on the method proposed by Duvillaret which was used to precisely determine the thickness of LiNbO3, the approach to measuring the absorption coefficient spectra of glutamine and histidine in frequency range from 0.3 to 2.6 THz(1 THz = 10(12) Hz) was improved in this paper. In order to validate the correctness of this absorption spectrum, we designed a series of experiments to compare the linearity of absorption coefficient belonging to one kind amino acid in different concentrations. The results indicate that as agreed by Lambert-Beer's Law, absorption coefficient spectrum of amino acid from the improved algorithm performs better linearity with its concentration than that from the common algorithm, which can be the basis of quantitative analysis in further researches.

In the present paper, using UV CCD optical multi-channel analyzer, the solar ultraviolet radiation spectra under the conditions of cloud cover were measured, and the impact of clouds on the solar ultraviolet radiation spectra were studied mostly. The results of spectral analysis showed that the intensity of solar ultraviolet radiation spectra was weakened by the clouds. The solar ultraviolet radiation spectral intensity attenuation depended on the wavelength and decreased with decreasing wavelength. The greater the cloud cover, the stronger the attenuation, The solar ultraviolet radiation spectral intensity at wavelengths below 315 nm was affected relatively less by the cloud cover. These results have more important practical applications. When we use solar ultraviolet radiation spectrum to study the atmospheric composition, we should choose the spectral band that is less affected by the atmospheric environment.

A novel approach to retrieving atmosphere NO2 slant column density is described, in which the sunlight scattered in the zenith direction and the skylight are used as the light sources. The slant column density of the same azimuth but different obliquities, which are between 0.5 x 10(16) and 11 x 10(16) molecule x cm(-2), with the angle from 85 degrees to 10 degrees, as well as that of the same obliquity but different azimuths, which are between 10(16) and 10(17) molecule cm(-2), were calculated. The study indicates that the results have good correlation with real atmosphere status. The angle spatial distribution could be embodied by the difference of NO2 slant column density in different azimuths and obliquities. The reference spectrum and sample spectrum were collected with the same instrument at the same time, so the measurement accuracy has been improved. This method favored not only real-time monitoring NO2 content of space arbitrary direction, especially near the ground NO2 pollution emergencies, but also overcast and rainy areas where it is very difficult to collect good direct solar spectrum.

The secondary structure of winter wheat bran antifreeze protein was analyzed by FTIR and CD spectra. The characteristic peaks of the secondary structure of the winter wheat bran antifreeze protein were overlapped from the FTIR analysis. The overlapped peaks of amide I and III of the winter wheat bran antifreeze protein were fitted by the Gauss peak to show the characteristic peaks of the alpha-helix, beta-sheet, beta-turn and random coil. The CD spectrum was evaluated by the Chen-Yang principle and analyzed by the least squares method. Furthermore, the difference between the two analyses was discussed. The final results showed that the alpha-helix, beta-sheet, beta-turn and random coil of the winter wheat bran antifreeze protein was 15.05%-15.87%, 36.00%-36.92%, 17.31%-17.75%, and 30.303-30.82%, respectively. The result would be helpful to the study of the antifreeze mechanism of the winter wheat bran antifreeze protein.

The solar ultraviolet irradiance spectrum in Chengdu area from March to July in 2006 was observed with an ultraviolet CCD optical multi-channel analyzer. According to the observation results, some analysis of the basic characteristics was made. The analysis of the solar ultraviolet irradiance spectrum showed that the solar ultraviolet irradiance is weak in the morning and in the evening but strong at noon, reaches the strongest point in June, and reversely correlates with the change in SZA (solar zenith angle); the ratio of irradiance flux of UVB to UVA is less than 0.04, and usually, the ratio in the afternoon is bigger than that in the morning in sunny days; Fogs can cause the ratio to increase, the reason is that fogs show stronger influence on attenuation of UVA than UVB; Clouds absorbed the solar ultraviolet irradiance greatly.

The present paper reports a new type of ultraviolet CCD optical multi-channel analyzer and its application to detecting solar ultraviolet irradiance spectrum. Spectral detecting range of 200-1 100 nm, spectral resolution of 0.1 nm and detecting sensitivity of 0.02 lx were reached in this instrument. The solar spectra of UVB and UVA were measured in real time in Chengdu area. The measurement results have good correlation with the detection using normal solar ultraviolet irradiance detector. Primary analysis on the detection results of solar spectra in UVB and UVA indicated that in the morning and in the afternoon the irradiance of solar ultraviolet is smaller than that at noon, and reverse correlation holds for the change of SZA (Solar Zenith Angle). In different wavelength interval of UVA and UVB, generally, the radiation flux of long wavelength is greater than that of short. Clouds and aerosols in the atmosphere have important influence on ultraviolet irradiance.

The fluorescence property of DCM in water solution with added different concentration of SDS is reported. With increasing the concentration of SDS in water, the solubility of DCM and the fluorescence intensity increase. When the concentration of SDS increases from 0.025 to 0.5 mol x L(-1), the maximum fluorescence relative intensity is enhanced by a factor of 95. A powerful dye laser at wavelength of 648 nm was generated in the solution of DCM in water with SDS exited by a 532 nm laser. It shifts 13 nm compared with the dye laser wavelength of the solution of DCM in ethanol. And enhancement of SRS of C6H6 was achieved both in the solution of DCM in water with SDS and in the solution of DCM in ethanol. The result is that the second, the third and the fourth order Stokes of C6H6 are all enhanced. But the former mainly enhances the fourth order Stokes (632 nm) and the enhancement gain coefficient is 8.5, while the latter mainly enhances the third order Stokes (595 nm) and the enhancement gain coefficient is 2.5. The mechanism of solubility, fluorescence enhancement and its possible application are discussed.