DEFORMATION ANALYSIS OF LASER SPECTRA BASEDON S_R DECOMPOSITION THEOREM

In the Fourier spectral analyzer, the Fourier spectra or the Fraunhofer diffraction pattern of an image is formed on the back focal plane when a laser beam is directed on the image lying on the front focal plane. If the image is deformed, its Forier spectra are also subjected to change. Therefore the change of the Fourier spectra provides a particular beautiful insight into the deformation of that image. Through proposing the corresponding relationship between the image and its spectra, and analyzing the change of Fourier spectra, the deformation of the image can be obtained. Based on Fourier optical theory and S-R decomposition theorem of finite deformation, in this paper, a state of the art deformation measurement technique is presented by using laser spectral analysis. The theoretical foundation of this new technique related to mathematics and optics, experimental principle and the technique of automatic recognizing and processing of rile deformed spectral image is discussed. The paper is as a special commemoration and memorial to the death anniversary of Professor Chen Zhida (1927 similar to 1998) , who initially proposed the above academic idea in early 80s.

UV–visible spectral characterization and density functional theory simulation analysis on laser-induced crystallization of amorphous silicon thin films

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.

Quantum Chemistry Study on Structures of Cluster Ions Nb_(n)S_(m)^(±)Generated by Laser Mass Spectra

ccording to the chemical bond theory we designed geometric structures ofcluster ions Nb_nS generated by laser ablation and calculated their electronic struc-tures using DV-X_a method of quantum chemistry. The results show that with theincrease of the cluster size the structures of the cluster ions change from a single-chain to a double-chain, then to a planar-net, and linking up to a net at Nb_3. Thenegative cluster ions tend to form a divergent configuration due to the extra chargeson it.

IR Spectra Analysis of SiO_2-TiO_2-GeO_2 Gel Glass of CO_2 Laser Transmitting Hollow Waveguide

Both titanium and germanium were introduced into silicon dioxide system by sol-gel method to move its region of anomalous dispersion caused by IR resonance absorption towards the wavelength of CO 2 laser.It is indicated by IR absorption spectra that as the content of SiO 2 decreases in this glass system TiO 2 and GeO 2 tends to exist in their own phases.As for the gel glass with a composition of 40SiO 2·30TiO 2·30GeO 2,when the temperature is below 600℃,germanium atoms exist mainly in Ge-O-Ge bonds.With the temperature increasing from 800℃ to 1000℃, titanium atoms in Si-O-Ti bonds almost transform into Ti-O-Ti bonds.Furthermore,a large number of Si-O-Ti and Si-O-Ge bonds formed when the temperature approaches 800℃,which makes a notable IR absorption band round the wavelength of CO 2 laser.Therefore, sol-gel based SiO 2-TiO 2-GeO 2 gel glass is a candidate material for CO 2 laser hollow waveguide.

X-RAY EMISSION SPECTRA FROM LASER-PRODUCED COBALT PLASMA

Based on theoretical calculations by our non-relativistic configuration interaction computer code,we have successfully identified the x-ray spectra from the cobalt plasma produced by high-power laser.Here we focus on the spectra consisting of x-ray line emission from the N-like and C-like ions.Many new x-ray lines have been identified.

Spectra-assisted laser focusing in quantitative analysis of laser-induced breakdown spectroscopy for copper alloys

Laser-induced breakdown spectroscopy(LIBS)is a capable technique for elementary analysis,while LIBS quantitation is still under development.In quantitation,precise laser focusing plays an important role because it ensures the distance between the laser and samples.In the present work,we employed spectral intensity as a direct way to assist laser focusing in LIBS quantitation for copper alloys.It is found that both the air emission and the copper line could be used to determine the position of the sample surface by referencing the intensity maximum.Nevertheless,the fine quantitation was only realized at the position where the air emission(e.g.O(I)777.4 nm)reached intensity maximum,and also in this way,a repeatable quantitation was successfully achieved even after 120 days.The results suggested that the LIBS quantitation was highly dependent on the focusing position of the laser,and spectra-assisted focusing could be a simple way to find the identical condition for different samples’detection.In the future,this method might be applicable in field measurements for LIBS analysis of solids.

High Resolution Laser Excitation Spectra and Franck-Condon Factors of A^(2)Π-X^(2)∑^(+) Electronic Transition of MgF

Magnesium monofluoride(MgF)is proposed as an ideal candidate radical for direct laser cooling.Here,the rotationally resolved laser spectra of MgF for the A^(2)Π-X^(2)∑^(+) electronic transition system were recorded by using laser induced fluorescence technique.The MgF radicals were produced by discharging SF_(6)/Ar gas mixtures between the tips of two magnesium needles in a supersonic jet expansion.We recorded a total of 19 vibrational bands belonging to three sequences of Δv=0,±1 in the region of 348-370 nm.Accurate spectroscopic constants for both X^(2)∑^(+) and A^(2)Π states are determined from rotational analysis of the experimental spectra.Spectroscopic parameters,including the Franck-Condon factors(FCFs),are determined from the experimental results and the Rydberg-Klein-Rees(RKR)calculations.Significant discrepancies between the experimentally measured and RKR-calculated FCFs are found,indicating that the FCFs are nearly independent of the spin-orbit coupling in the A^(2)Π state.Potential energy curves(PECs)and FCFs determined here provide necessary data for the theoretical simulation of the laser-cooling scheme of MgF.

X-Ray and VUV Spectra from the Laser Plasma Produced with “Kanal-2” Facility

The paper presents experimental results obtained on “Kanal-2” facility. Laser radiation focusing on the surface of plane magnesium targets created the high temperature plasma, which emitted X-ray and vacuum ultraviolet (VUV) radiation. This radiation spectrum was investigated with two spectrographs: the mica crystal spectrograph (working range 8.2 ? - 9.6 ?) and the grazing incidence VUV spectrograph (working rage 30 ? - 130 ?). A set of beryllium stepwise attenuators appended the diagnostic complex and allowed us to get an approximated picture of a continuous spectrum within the range of 2.2 ? - 6.2 ?. The estimation of the plasma electron temperature Te from the ratio between the intensity of the dielectronic satellites and the resonance line gives Te ~ 180 eV. The ratio between the intensity of the resonance and intercombination lines gives the electron density of the emitting zone ne ~ 2 × 1019 cm-3. Some lines observed within the spectral range of 8.5 ? - 9.1 ? belong to none of the transitions of Mg ions. Perhaps the observed spectrum is determined by the transitions in so-called hollow ions of Mg, i.e. in the ions with unfilled inner shells. The spectra obtained with the grazing incidence spectrograph and with the minimum-directioned discrepancy iteration method of spectrum reconstruction from the attenuation curve in the beryllium stepwise attenuators are also presented.

Time-resolved K-shell x-ray spectra of nanosecond laser-produced titanium tracer in gold plasmas

A study of a nanosecond laser irradiation on the titanium-layer-buried gold planar target is presented. The timeresolved x-ray emission spectra of titanium tracer are measured by a streaked crystal spectrometer. By comparing the simulated spectra obtained by using the FLYCHK code with the measured titanium spectra, the temporal plasma states, i.e.,the electron temperatures and densities, are deduced. To evaluate the feasibility of using the method for the characterization of Au plasma states, the deduced plasma states from the measured titanium spectra are compared with the Multi-1D hydrodynamic simulations of laser-produced Au plasmas. By comparing the measured and simulated results, an overall agreement for the electron temperatures is found, whereas there are deviations in the electron densities. The experiment–theory discrepancy may suggest that the plasma state could not be well reproduced by the Multi-1D hydrodynamic simulation, in which the radial gradient is not taken into account. Further investigations on the spectral characterization and hydrodynamic simulations of the plasma states are needed. All the measured and FLYCHK simulated spectra are given in this paper as datasets. The datasets are openly available at http://www.doi.org/10.57760/sciencedb.j00113.00032.

Angle-Resolved Electron Spectra of F^- Ions by Few-Cycle Laser Pulses

The above-threshold detachment of F- ions induced by a linearly polarized few-cycle laser pulse is investigated theoretically using the strong-field approximation model without considering the rescattering mechanism. We first derive an analytical form of transition amplitude for describing the strong-field photodetachment of F- ions. The integration over time in transition amplitude can be performed using the numerical integration method or the saddle-point （SP） method of Shearer et al. [Phys. Rev. A 88 （2013） 033415]. The validity of the SP method is carefully examined by comparing the energy spectra and photoelectron angular distributions （PADs） with those obtained from the numerical integration method. By considering the volume effect of a focused laser beam, both the energy spectra and the low-energy PADs calculated by the numerical integration method agree very well with the experimental results.

Effect of Laser Annealing on Permeability Spectra in Co-based Amorphous Ribbon

We investigated the variation of permeability spectra and relaxation frequency in Co-based amorphous ribbon annealed by pulsed Nd:YAG laser at various annealing energy Ea. The complex permeability spectra varies sensitively with the annealing energy, where the spectra could be decomposed into two contributions from domain wall motion,μdw(f) and rotational magnetization μrot(f) by analyzing the measured spectra as a function of driving ac field amplitude. The magnitude of μdw(f) and μrot(f) in dc limit shows maximum at Ea = 176 mJ. The maximum relaxation frequency for rotational magnetization, determined by μ'(f) curve, is about 700 kHz at Ea=62 mJ but that for wall motion is about 26 kHz at 230 mJ. These variations reflect the increase of magnetic softness and microstructural change by the annealing.

Diagnostics of laser-induced plasma on carbon-based polymer material using atomic and molecular emission spectra

Time-integrated optical emission analysis of laser-induced plasma on Teflon is presented.Plasma was induced under atmospheric pressure air using transversely excited atmospheric CO_(2) laser pulses.Teflon is a C-based polymer that is,among other things,interesting as a substrate for laser-induced breakdown spectroscopy analysis of liquid samples.This study aimed to determine the optimal experimental conditions for obtaining neutral and ionized C spectral lines and C2 and CN molecular band emission suitable for spectrochemical purposes.Evaluation of plasma parameters was done using several spectroscopic techniques.Stark profiles of appropriate C ionic lines were used to determine electron number density.The ratio of the integral intensity of ionic-to-atomic C spectral lines was used to determine the ionization temperature.A spectral emission of C2 Swan and CN violet bands system was used to determine the temperature of the colder,peripheral parts of plasma.We critically analyzed the use of molecular emission bands as a tool for plasma diagnostics and suggested methods for possible improvements.

Raman Spectra of Laser Crystals NAB and NYAB and the Ligand Vibrations of Their Active Ions

The lattice vibration mode of the laser crystals NAB and NYAB are measured by Raman spectra method and the possible effects of the BO3 and NdO6 vibration modes on the non-radiative transition of the active ions are discussed.

MEBO治疗Spectra双脉冲激光祛斑术后创面的临床疗效

目的观察Spectra双脉冲激光祛斑术后创面应用湿润烧伤膏（Moist Exposed Burn Ointment,MEBO）治疗的临床效果。方法将200例采用Spectra双脉冲激光祛斑术祛斑的患者随机分为治疗组和对照组,每组100例。治疗组治疗结束后用冰袋敷面0.5~1.0 h,然后将MEBO均匀涂抹于创面,厚约1mm,每6 h换药1次,3 d后停用,并每日以冷水洁面;对照组治疗结束后仅用冰袋冰敷0.5~1.0 h,不做其他处理,保持创面清洁干燥,3 d后每日以冷水洁面,对比观察两组患者的疼痛情况、创面愈合时间。结果治疗组的疼痛情况（无痛81例,疼痛19例）与对照组（无痛25例,疼痛75例）相比,P〈0.01,差异具有统计学意义;治疗组的创面平均愈合时间（9.53 d）与对照组（10.65 d）相比,P〈0.01,差异具有统计学意义。结论湿润烧伤膏（MEBO）治疗Spectra双脉冲激光祛斑术后创面,疗效显著,具有止痛效果好、创面愈合时间短等作用。

Spectra双脉冲激光对黄褐斑抗氧化功能、甲皱微循环的影响

目的:探讨Spectra双脉冲激光祛斑术对黄褐斑患者抗氧化功能、甲皱微循环的影响。方法:105例黄褐斑患者采用随机数字表法分为观察组(n=53)和对照组(n=52),对照组接受常规治疗,观察组在常规治疗的基础上接受Spectra双脉冲激光祛斑术治疗。比较两组疗效,治疗后血清氧化应激指标、甲皱微循环积分、生活质量改善情况及患者美观满意度。结果:观察组总有效率为92.45%,显著高于对照组的76.92%(P<0.05);治疗后,两组超氧化物歧化酶(Super oxide dismutase,SOD)水平明显升高,而丙二醛(Malondialdehyde,MDA)、一氧化氮(Nitric oxide,NO)水平、甲皱微循环积分(血流速度、管袢形态、袢周状态及总积分)、黄褐斑生活质量评分(Melasma quality of life scale,MelasQOL)及皮肤病生活质量指数(Dermatology life quality index,DLQI)明显降低(P<0.05),且观察组SOD水平显著高于对照组,MDA、NO水平、甲皱微循环积分、MelasQOL评分、DLQI指数均显著低于对照组(P<0.05);观察组美观满意度为90.57%,优于对照组的71.15%(P<0.05)。结论:采用Spectra双脉冲激光祛斑术治疗黄褐斑,能通过调节患者SOD、MDA、NO水平,增强其抗氧化功能,促进甲皱微循环改善,继而提高治疗效果,改善患者生活质量,有较高的临床应用价值。

Crystal growth, spectroscopic characteristics, and Judd–Ofelt analysis of Dy:Lu_2O_3 for yellow laser

Dy：Lu2O3 was grown by the float-zone （Fz） method. According to the absorption spectrum, the Judd-Ofelt （JO） parameters Ω2, Ω4, and Ω6 were calculated to be 4.86 × 10-20 cm2, 2.02 × 10-20 cm2, and 1.76 ×10-20 cm2, respectively. The emission cross-section at 574 nm corresponding to the 4F9/2 →6H13/2 transition was calculated to be 0.53 ×10 20 cm2. The yellow （4F9/2 →6H13/2 transition） to blue （4F9/2 →6H15/2 transition） intensity ratio ranges up to 12.9. The fluorescence lifetime of the 4F9/2 energy level was measured to be 112.1 μs. These results reveal that Dy：Lu2O3 is a promising material for use in yellow lasers.

Photoionization of NaK molecule with a double-well potential in femtosecond pump-probe pulse laser fields

The method of time-dependent quantum wave packet dynamics is used to calculate the femtosecond pump-probe photoelectron spectra and study the wave packet dynamic processes of the double-minimum potential state 6^1∑^＋ of NaK in intense laser fields. The evolutions of the wave packet and the photoelectron energy spectra with time and internuclear distance are described in detail. The wave packet dynamic information of the 6^1∑^＋ state can be extracted from the photoelectron energy spectra.

The dissociation pathways of N_2^+ in intense femtosecond laser fields

Using a neutral N2 beam as target, this paper studies the dissociation of N2^＋ in intense femtosecond laser fields （45 fs, ～ 1 × 10^16 W/cm^2） at the laser wavelength of 800 nm based on the time-of-flight mass spectra of N＋ fragment ions. The angular distributions of N^＋ and the laser power dependence of N^＋ yielded from different dissociation pathways show that the dissociation mechanisms mainly proceed through the couplings between the metastable states （A, B and C） and the upper excited states of N^＋.A coupling model of light-dressed potential energy curves of N2^＋ is used to interpret the kinetic energy release of N^＋.

Crystal growth and spectral properties of Tb：Lu2O3

The crystal growth,x-ray diffraction pattern,absorption spectrum,emission spectrum,and fluorescence lifetime of a Tb：Lu2O3 single crystal were studied.Excited at 483 nm,the peak absorption cross-section was calculated to be 3.5×10（-22）cm2,and the full width at half maximum was found to be 2.85 nm.The Judd-Ofelt（J-O）intensity parameters 2,4,and 6 were computed to be 3.79×10（-20）cm2,1.30×10（-20）cm2,and 1.08×10（-20）cm2,with a spectroscopic quality factor 4/6 being 1.20.The emission cross-sections of green emission around 543 nm and yellow emission around 584 nm were calculated to be 9.43×10（-22）cm2 and 1.32×10（-22）cm2,respectively.The fluorescence lifetimeτexp of -5D4 was fitted to be 1.13 ms.The data suggest that the Tb：Lu2O3 crystal could be a potential candidate for green and yellow laser operation.

Improvement of laser damage thresholds of fused silica by ultrasonic-assisted hydrofluoric acid etching

Polished fused silica samples were etched for different durations by using hydrofluoric（HF） acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular structure parameters before and after the etching process were characterized by using a fluorescence microscope and infrared（IR） spectrometer, respectively. The laser induced damage thresholds（LIDTs） of the samples were measured by using pulsed nanosecond laser with wavelength of 355 nm. The results showed that surface and subsurface polishing residues can be effectively reduced by the acid etching process, and the LIDTs of fused silica are significantly improved. The etching effects increased with the increase of the HF concentration from 5 wt.% to 40 wt.%. The amount of polishing residues decreased with the increase of the etching duration and then kept stable. Simultaneously, with the increase of the etching time, the mechanical strength and molecular structure were improved.