The predominant spectral blueshifting of a sub-picosecond UV laser pulse induced by ultrafast ionization of noble gases was investigated. Spectral measurements were made at various gas densities. Typical quasi-periodi...The predominant spectral blueshifting of a sub-picosecond UV laser pulse induced by ultrafast ionization of noble gases was investigated. Spectral measurements were made at various gas densities. Typical quasi-periodic structures in the blueshifted spectrum were obtained. The observations were in connection with the so-called self-phase modulation of laser pulses in the ultrafast ionization process which was simply simulated with an ADK （Ammosov-Delone-Krainov） ionization model. Some quantitative information can be deduced from the measurements and calculations.展开更多
The parametric optimization of the Ne-CuBr UV laser excited by longitudinal pulsed discharge is analysed by using a self-consistent kinetic model. Consistent characteristics of the optimization process are obtained by...The parametric optimization of the Ne-CuBr UV laser excited by longitudinal pulsed discharge is analysed by using a self-consistent kinetic model. Consistent characteristics of the optimization process are obtained by comparing with the experimental results. Simulation results show that neon ions come into being along with considerable depletion of the ground-state copper atoms. And the optimization of the discharge tube diameter is the tradeoff between the specific output photon density and the total active volume. Both the optimal neon gas pressure and the optimal reservoir temperature result from the balance between the neon ion density and the ground-state copper atom density to arrive at a maximum of their product.展开更多
In this paper, the stereoselective homogeneous catalysis polymerization of phenylacetylene by using two kinds of catalysts W(CO)_5CH_3I and W(CO)_4I_2 produced from UV laser photolysis of W (CO)_6 in CH_3I, I_2—C_6H_...In this paper, the stereoselective homogeneous catalysis polymerization of phenylacetylene by using two kinds of catalysts W(CO)_5CH_3I and W(CO)_4I_2 produced from UV laser photolysis of W (CO)_6 in CH_3I, I_2—C_6H_6 and CHI_3—C_6H_6 respectively was studied. The effects of laser energy, laser irradiation time and lifetime of catalyst on the polymerization of phenylacetylene were discussed. The photoproducts of W (CO)_6 in CH_3I, I2—C_6H_6 and CHI_3—C_6I_6 were determined by IR spectra. The structures of polyphenylacetylene obtained by W (CO)_5CH_3I and W (CO)_4I_2 catalysts were characterized by IR spectra and ~1H NMR spectra.展开更多
Time-resolved IR absorption spectroscopy has been used to atudy the photochemistry of W(CO)_6 in cyclohexane, carbon tetrachloride, and the mixture of carbon tetrachloride and cyelohexane. The reastion of photolytical...Time-resolved IR absorption spectroscopy has been used to atudy the photochemistry of W(CO)_6 in cyclohexane, carbon tetrachloride, and the mixture of carbon tetrachloride and cyelohexane. The reastion of photolytically generated W(CO)_5. C_6H_(12) with CCl_4 was investigated. An intermediate with a lifetime of about 0.5ms, presumably attributed as W(GO)_5.CCl_4, was first observed.展开更多
There has recently been great interest in ablative photodecomposition(APD), notably in pulsed UV laser treatment on polymers, for modification of physical and chemical properties, such as dyeability, printability, adh...There has recently been great interest in ablative photodecomposition(APD), notably in pulsed UV laser treatment on polymers, for modification of physical and chemical properties, such as dyeability, printability, adhesion, Iuster and many more. Very little attention was focused, however, on the property of wetting behaviour,which is one of the most fundamental properties in affecting polymer science. Poly(ethylene terephthalate) (PET) fibers drawn to two different draw ratios and under two temperatures, and three white knitted polyester fabrics made of 100% PET fibre were used to investigate their wetting behaviour due to excimer laser treatment.Experiments like water contact angle measurement, vertical drop test and moisture regain were conducted upon samples and all results give the same conclusion that laser treatment increases the hydrophobicity of all samples tested. Scanning electron microscope (SEM) observation reveals how the morphological modification of polymers by laser treatment is展开更多
An analytical model describing the physical relations of a UV-based process for halogenation of polymeric surfaces is presented. The process allows, depending on the parameters, a local halogenation with sharp edges a...An analytical model describing the physical relations of a UV-based process for halogenation of polymeric surfaces is presented. The process allows, depending on the parameters, a local halogenation with sharp edges at the interfaces to areas where no halogenation is desired. This is achieved via a nonreactive halogen-containing gaseous precursor and a UV source providing photons which dissociate the precursor photolytically. Thus, only where the UV photons affect the precursor, halogens are generated and the polymer is being halogenated.展开更多
Multi-beam laser processing is a very popular method to improve processing efficiency. For this purpose, a compact and stable multi-beam pulsed 355 nm ultraviolet(UV) laser based on a micro-lens array(MLA) is presente...Multi-beam laser processing is a very popular method to improve processing efficiency. For this purpose, a compact and stable multi-beam pulsed 355 nm ultraviolet(UV) laser based on a micro-lens array(MLA) is presented in this Letter. It is worth noting that the MLA is employed to act as the spatial splitter as well as the coupling lens. With assistance of the MLA,the 1064 nm laser and 532 nm laser are divided into four sub-beams and focused at different areas of the third-harmonic generation(THG) crystal. As a result, the multi-beam pulsed 355 nm UV laser is successfully generated inside the THG crystal. The measured pulse widths of four sub-beams are shorter than 9 ns. Especially, the generated four sub-beams have good long-term power stability benefitting from the employed MLA. We believe that the generated stable multi-beam355 nm UV laser can meet the requirement of high-efficiency laser processing, and the presented method can also pave the way to generate stable and long-lived multi-beam UV lasers.展开更多
A new resistless etching method has been de-veloped for Silicon wafers. This new method uses an aqueous solution consisting of hydrogen peroxide (H2O2) and hydro-gen fluoride (HF) as the activating etchants. A 193 nm ...A new resistless etching method has been de-veloped for Silicon wafers. This new method uses an aqueous solution consisting of hydrogen peroxide (H2O2) and hydro-gen fluoride (HF) as the activating etchants. A 193 nm ArF excimer laser and a 266 nm fourth harmonic generation Nd:YAG laser were used as the photon sources. Results showed that pattern etching has been achieved without any photoresist film. In the case of the 193 nm laser, the optimal etching appeared at a 1.3 H2O2/HF ratio, where an etchdepth of 210 nm was achieved with a fluence of 29 mJ/cm2 and shot number of 10000. At the same conditions, the etch depth with H2O2 and HF solution was three times of that by using H2O and HF mixture. In the case of the 266 nm Nd : YAG laser, the optimal etching appeared at twice ratio of H2O2/HF, where the etch depth of 420 nm was achieved witha fluence of 12 mJ/cm2 and shot number of 30000. Results showed that the etch effect of the 266 nm Nd : YAG laser was more desirable than that of the 193 nm ArF展开更多
HO radical is an aggressive reagent to abstract hydrogen from diverse substitutes and lead them to degradation, however, in reaction of active oxygen species with lignins, complex phenolic polymers, in dispersed ligno...HO radical is an aggressive reagent to abstract hydrogen from diverse substitutes and lead them to degradation, however, in reaction of active oxygen species with lignins, complex phenolic polymers, in dispersed lignocellulose such as pulp for environment-benign delignification, HO radicals should be eliminated as more as possible to prevent cellulose from unfavorably concomitant degradation. A reaction system of O3 is constructed under UV laser flash irradiation, and HO radicals are controlled efficiently by it. A new mechanism is proposed, for the first time, that O radicals generated from reaction of O3 with UV laser flash irradiation might be the contributor to scavenge HO radicals.展开更多
With the pulsed laser deposition （PLD） method, amorphous 80GeS2-15Ga2S3-5CdS chalcogenide film was deposited on glassy substrate. Obvious second harmonic generation （SHG） was observed in the ultraviolet （UV）-pol...With the pulsed laser deposition （PLD） method, amorphous 80GeS2-15Ga2S3-5CdS chalcogenide film was deposited on glassy substrate. Obvious second harmonic generation （SHG） was observed in the ultraviolet （UV）-polarized film and the SHG intensity increased with the increase in single pulse energy and irradiation time. Through Raman spectra and transmission spectra, the mechanism of SHG was studied. The experimental results demonstrated that effective electron traps and hole traps were generated in the UV- polarized film. The energy of electrons and holes was using up due to the collision with other particles and crystal fields during their movement and finally they were captured by the traps and fixed, which made the electric charge distribution nonuniform in the film and destroyed the spatial isotropy. In the meantime, the center of positive and negative charges separated and a built-in electric field was formed which generated the optical second-order nonlinearity of the film.展开更多
The effect of laser energy density on the crystallization of hydrogenated intrinsic amorphous silicon （a-Si：H） thin films was studied both theoretically and experimentally. The thin films were irritated by a freque...The effect of laser energy density on the crystallization of hydrogenated intrinsic amorphous silicon （a-Si：H） thin films was studied both theoretically and experimentally. The thin films were irritated by a frequency-doubled （λ= 532 nm） Nd：YAG pulsed nanosecond laser. An effective density functional theory model was built to reveal the variation of bandgap energy influenced by thermal stress after laser irradiation. Experimental results establish correlation between the thermal stress and the shift of transverse optical peak in Raman spectroscopy and suggest that the relatively greater shift of the transverse optical （TO） peak can produce higher stress. The highest crystalline fraction （84.5%） is obtained in the optimized laser energy density （1000 mJ/cm2） with a considerable stress release. The absorption edge energy measured by the UV- visible spectra is in fairly good agreement with the bandgap energy in the density functional theory （DFT） simulation.展开更多
The multi-element components of low alloy steel were quantified by using laser-induced breakdown spectroscopy (LIBS) in deep UV. The Nd:YAG pulsed laser was used to produce plasma. The spectrum was simultaneously obta...The multi-element components of low alloy steel were quantified by using laser-induced breakdown spectroscopy (LIBS) in deep UV. The Nd:YAG pulsed laser was used to produce plasma. The spectrum was simultaneously obtained by deep UV spectrometer. This paper studied the influence of experiment parameters on LIBS spectral intensity, such as delay, energy of laser, and the distance between the focusing lens and the surface of the sample. With the optimal expe- riment parameters, the characteristic lines of C, Ni, Si, Cr and Cu contained in low alloy steel were selected for quantit- ative analysis and the calibration curves of these elements were obtained. The linear correlation coefficient was good. Using the calibration curves to quantitative analysis for the sample 05-d, and the relative error of analytical results is less than 10% for most elements.展开更多
UV-Vis absorption and fluorescence spectroscopy are used to test the quality and changes in the composition of extra virgin olive oil (EVOO) and canola oil (CO) with temperature. The increase of temperature caused a c...UV-Vis absorption and fluorescence spectroscopy are used to test the quality and changes in the composition of extra virgin olive oil (EVOO) and canola oil (CO) with temperature. The increase of temperature caused a change in the molecular structures of both types of oils seen as a gradual decrease of intensity amplitudes of absorption and fluorescence signals. A significant alteration occurred at ≈200°C where almost the main spectra of pheophytin-a, b, carotenoids, lutein and vitamin E in EVOO and linoleic acid and oleic acid in CO disappeared. An independent experiment showed the output of laser changes linearly with the input in oil at constant temperature (i.e., room temperature) where the transmission values of ≈33% and ≈75% are determined for EVOO and CO respectively. However, the transmission through a heated oil exhibited a non-linear behaviour which indicates the molecular optical response to thermal changes. The effect of storage time and adulteration of oils were also evaluated.展开更多
基金National Natural Science Foundation of China(Nos.10474081,10735050)National Basic Research Program of China(973 Program)(No.2007CB815102)
文摘The predominant spectral blueshifting of a sub-picosecond UV laser pulse induced by ultrafast ionization of noble gases was investigated. Spectral measurements were made at various gas densities. Typical quasi-periodic structures in the blueshifted spectrum were obtained. The observations were in connection with the so-called self-phase modulation of laser pulses in the ultrafast ionization process which was simply simulated with an ADK （Ammosov-Delone-Krainov） ionization model. Some quantitative information can be deduced from the measurements and calculations.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10574111 and 10374081)
文摘The parametric optimization of the Ne-CuBr UV laser excited by longitudinal pulsed discharge is analysed by using a self-consistent kinetic model. Consistent characteristics of the optimization process are obtained by comparing with the experimental results. Simulation results show that neon ions come into being along with considerable depletion of the ground-state copper atoms. And the optimization of the discharge tube diameter is the tradeoff between the specific output photon density and the total active volume. Both the optimal neon gas pressure and the optimal reservoir temperature result from the balance between the neon ion density and the ground-state copper atom density to arrive at a maximum of their product.
文摘In this paper, the stereoselective homogeneous catalysis polymerization of phenylacetylene by using two kinds of catalysts W(CO)_5CH_3I and W(CO)_4I_2 produced from UV laser photolysis of W (CO)_6 in CH_3I, I_2—C_6H_6 and CHI_3—C_6H_6 respectively was studied. The effects of laser energy, laser irradiation time and lifetime of catalyst on the polymerization of phenylacetylene were discussed. The photoproducts of W (CO)_6 in CH_3I, I2—C_6H_6 and CHI_3—C_6I_6 were determined by IR spectra. The structures of polyphenylacetylene obtained by W (CO)_5CH_3I and W (CO)_4I_2 catalysts were characterized by IR spectra and ~1H NMR spectra.
文摘Time-resolved IR absorption spectroscopy has been used to atudy the photochemistry of W(CO)_6 in cyclohexane, carbon tetrachloride, and the mixture of carbon tetrachloride and cyelohexane. The reastion of photolytically generated W(CO)_5. C_6H_(12) with CCl_4 was investigated. An intermediate with a lifetime of about 0.5ms, presumably attributed as W(GO)_5.CCl_4, was first observed.
文摘There has recently been great interest in ablative photodecomposition(APD), notably in pulsed UV laser treatment on polymers, for modification of physical and chemical properties, such as dyeability, printability, adhesion, Iuster and many more. Very little attention was focused, however, on the property of wetting behaviour,which is one of the most fundamental properties in affecting polymer science. Poly(ethylene terephthalate) (PET) fibers drawn to two different draw ratios and under two temperatures, and three white knitted polyester fabrics made of 100% PET fibre were used to investigate their wetting behaviour due to excimer laser treatment.Experiments like water contact angle measurement, vertical drop test and moisture regain were conducted upon samples and all results give the same conclusion that laser treatment increases the hydrophobicity of all samples tested. Scanning electron microscope (SEM) observation reveals how the morphological modification of polymers by laser treatment is
文摘An analytical model describing the physical relations of a UV-based process for halogenation of polymeric surfaces is presented. The process allows, depending on the parameters, a local halogenation with sharp edges at the interfaces to areas where no halogenation is desired. This is achieved via a nonreactive halogen-containing gaseous precursor and a UV source providing photons which dissociate the precursor photolytically. Thus, only where the UV photons affect the precursor, halogens are generated and the polymer is being halogenated.
基金supported by the National Natural Science Foundation of China (Nos. 61975100 and 62027821)Program for the Innovative Talents of High Education Institutions of ShanxiFund for Shanxi “1331 Project” Key Subjects Construction
文摘Multi-beam laser processing is a very popular method to improve processing efficiency. For this purpose, a compact and stable multi-beam pulsed 355 nm ultraviolet(UV) laser based on a micro-lens array(MLA) is presented in this Letter. It is worth noting that the MLA is employed to act as the spatial splitter as well as the coupling lens. With assistance of the MLA,the 1064 nm laser and 532 nm laser are divided into four sub-beams and focused at different areas of the third-harmonic generation(THG) crystal. As a result, the multi-beam pulsed 355 nm UV laser is successfully generated inside the THG crystal. The measured pulse widths of four sub-beams are shorter than 9 ns. Especially, the generated four sub-beams have good long-term power stability benefitting from the employed MLA. We believe that the generated stable multi-beam355 nm UV laser can meet the requirement of high-efficiency laser processing, and the presented method can also pave the way to generate stable and long-lived multi-beam UV lasers.
文摘A new resistless etching method has been de-veloped for Silicon wafers. This new method uses an aqueous solution consisting of hydrogen peroxide (H2O2) and hydro-gen fluoride (HF) as the activating etchants. A 193 nm ArF excimer laser and a 266 nm fourth harmonic generation Nd:YAG laser were used as the photon sources. Results showed that pattern etching has been achieved without any photoresist film. In the case of the 193 nm laser, the optimal etching appeared at a 1.3 H2O2/HF ratio, where an etchdepth of 210 nm was achieved with a fluence of 29 mJ/cm2 and shot number of 10000. At the same conditions, the etch depth with H2O2 and HF solution was three times of that by using H2O and HF mixture. In the case of the 266 nm Nd : YAG laser, the optimal etching appeared at twice ratio of H2O2/HF, where the etch depth of 420 nm was achieved witha fluence of 12 mJ/cm2 and shot number of 30000. Results showed that the etch effect of the 266 nm Nd : YAG laser was more desirable than that of the 193 nm ArF
基金This work was supported by the Research Fund of Ministry of Education for Academic Institutionof Doctoral Education (Grant No. 2000056109) Research Fund for Returned Overseas Chinese Scholars (Grant No. 2000479).
文摘HO radical is an aggressive reagent to abstract hydrogen from diverse substitutes and lead them to degradation, however, in reaction of active oxygen species with lignins, complex phenolic polymers, in dispersed lignocellulose such as pulp for environment-benign delignification, HO radicals should be eliminated as more as possible to prevent cellulose from unfavorably concomitant degradation. A reaction system of O3 is constructed under UV laser flash irradiation, and HO radicals are controlled efficiently by it. A new mechanism is proposed, for the first time, that O radicals generated from reaction of O3 with UV laser flash irradiation might be the contributor to scavenge HO radicals.
基金Funded by the National Natural Science Foundaition of China(Nos.51172169 and 61177084),NCET\(NCET-11-0687)the Fundamental Research Funds for the Central Universities(Wuhan University of Technology)
文摘With the pulsed laser deposition （PLD） method, amorphous 80GeS2-15Ga2S3-5CdS chalcogenide film was deposited on glassy substrate. Obvious second harmonic generation （SHG） was observed in the ultraviolet （UV）-polarized film and the SHG intensity increased with the increase in single pulse energy and irradiation time. Through Raman spectra and transmission spectra, the mechanism of SHG was studied. The experimental results demonstrated that effective electron traps and hole traps were generated in the UV- polarized film. The energy of electrons and holes was using up due to the collision with other particles and crystal fields during their movement and finally they were captured by the traps and fixed, which made the electric charge distribution nonuniform in the film and destroyed the spatial isotropy. In the meantime, the center of positive and negative charges separated and a built-in electric field was formed which generated the optical second-order nonlinearity of the film.
基金Project supported by the Shanghai Leading Academic Disciplines,China(Grant No.S30107)
文摘The effect of laser energy density on the crystallization of hydrogenated intrinsic amorphous silicon （a-Si：H） thin films was studied both theoretically and experimentally. The thin films were irritated by a frequency-doubled （λ= 532 nm） Nd：YAG pulsed nanosecond laser. An effective density functional theory model was built to reveal the variation of bandgap energy influenced by thermal stress after laser irradiation. Experimental results establish correlation between the thermal stress and the shift of transverse optical peak in Raman spectroscopy and suggest that the relatively greater shift of the transverse optical （TO） peak can produce higher stress. The highest crystalline fraction （84.5%） is obtained in the optimized laser energy density （1000 mJ/cm2） with a considerable stress release. The absorption edge energy measured by the UV- visible spectra is in fairly good agreement with the bandgap energy in the density functional theory （DFT） simulation.
文摘The multi-element components of low alloy steel were quantified by using laser-induced breakdown spectroscopy (LIBS) in deep UV. The Nd:YAG pulsed laser was used to produce plasma. The spectrum was simultaneously obtained by deep UV spectrometer. This paper studied the influence of experiment parameters on LIBS spectral intensity, such as delay, energy of laser, and the distance between the focusing lens and the surface of the sample. With the optimal expe- riment parameters, the characteristic lines of C, Ni, Si, Cr and Cu contained in low alloy steel were selected for quantit- ative analysis and the calibration curves of these elements were obtained. The linear correlation coefficient was good. Using the calibration curves to quantitative analysis for the sample 05-d, and the relative error of analytical results is less than 10% for most elements.
文摘UV-Vis absorption and fluorescence spectroscopy are used to test the quality and changes in the composition of extra virgin olive oil (EVOO) and canola oil (CO) with temperature. The increase of temperature caused a change in the molecular structures of both types of oils seen as a gradual decrease of intensity amplitudes of absorption and fluorescence signals. A significant alteration occurred at ≈200°C where almost the main spectra of pheophytin-a, b, carotenoids, lutein and vitamin E in EVOO and linoleic acid and oleic acid in CO disappeared. An independent experiment showed the output of laser changes linearly with the input in oil at constant temperature (i.e., room temperature) where the transmission values of ≈33% and ≈75% are determined for EVOO and CO respectively. However, the transmission through a heated oil exhibited a non-linear behaviour which indicates the molecular optical response to thermal changes. The effect of storage time and adulteration of oils were also evaluated.
