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Isotope shifts in the spectrum of the neutral titanium atom
摘要： An investigation of 53 saturated absorption lines of titanium at wavelengths ranging from 695 to 1005 nm is performed. In addition, transitions 3d34s a5FJ → 3d34p y5FJ (J = 3, 4, 5) in the ultraviolet range are measured. The isotope lines of 46Ti, 48Ti, and 50Ti are clearly observed for 53 transitions. A facing target sputtering system containing a magnetic field is used as a sample cell of titanium in this experiment. The Zeeman effect in a hyperfine structure is calculated for the condition of an intermediate field approximation to determine the unperturbed line positions in the odd mass isotopes 47Ti and 49Ti. For all observed transitions, the King plot analysis is performed to determine the electronic factors of the field shift and specific mass shift.
关键词： Isotope Shift,Saturated absorption spectroscopy
更新于2025-09-19 17:15:36
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Synthesis of Cu2O/Carbon film/NiCoB-GO Heterostructure Photocathode for Efficient Photoelectrochemical Water Splitting
摘要： Photoelectrochemical (PEC) water splitting offers a promising way to convert solar energy to chemical energy. The electron transfer rate and surface-catalyzed ability toward hydrogen evolution reaction (HER) play the key roles in the efficiency of PEC water splitting. In this work, a Cu2O/Carbon film/NiCoB-GO heterostructure photocathode is fabricated. Among them, thickness-controllable carbon film served as the electron transport and protective layer with favourable optical property, NiCoB-GO amorphous catalyst displays the efficient performance towards HER in neutral condition. The optimized photocathode shows the PEC-HER performance with a photocurrent density of -2.9 mA/cm2 at 0 V vs. RHE, and it also presents better stability than bare Cu2O. This work provides a novel heterostructure photocathode for promoting solar-driven PEC water splitting efficiently.
关键词： Femtosecond transient absorption spectroscopy,Photoelectrochemical water splitting,Electron transport path,Carbon film,Amorphous catalyst
更新于2025-09-19 17:15:36
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Electron transfer between heterogeneous lanthanides in BaF2 crystals
摘要： Forward electron photo-transfer and reverse thermal transfer between divalent and trivalent heterogeneous lanthanides in barium fluoride crystals has been studied using optical absorption. In crystals activated by two heterogeneous lanthanides and grown in reducing conditions, one of the lanthanides becomes bivalent whereas the other lanthanide remains trivalent. Illumination of the crystal in the ultraviolet bands led to the transfer of electrons from divalent lanthalides (Eu, Yb, Sm) to trivalent ions (Ho, Nd, Dy, Tm, Sm, Yb). The thermal ionization energies to the conduction band of created lanthanides are determined from the thermal bleaching curves of absorption bands. The experimental energies are compared with the estimated energies of the Dorenbos model.
关键词： BaF2,level positions,electron phototransfer,urbach constant,lanthanide,absorption,spectroscopy
更新于2025-09-19 17:15:36
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Noninvasive blood glucose detection by Quantum Cascade Laser
摘要： Quantum Cascade Laser (QCL) was invented in late 90s as a promising mid-infrared light source and contributed to the field of industry, military, medicine, and biology. The room temperature operation, watt-level output power, compact size, and wide tuning capability of this laser advanced the field of noninvasive blood glucose detection by exploring transmission, absorption, and photoacoustic spectroscopy. This review provides a complete overview of the recent progress and technical details of these spectroscopy techniques, using QCL as an infrared light source for detecting blood glucose concentration for diabetic patients.
关键词： transmission spectroscopy,Quantum Cascade Laser,mid-infrared,noninvasive blood glucose detection,photoacoustic spectroscopy,absorption spectroscopy
更新于2025-09-19 17:13:59
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Determination of atomic oxygen state densities in a double inductively coupled plasma using optical emission and absorption spectroscopy and probe measurements
摘要： A collisional radiative model for fast estimation and monitoring of atomic oxygen ground and excited state densities and ?uxes in varying Ar:O2 mixtures is developed and applied in double inductively coupled plasma source at a pressure of 5 Pa and incident power of 500 W. The model takes into account measured line intensities of 130.4 nm, 135.6 nm, 557.7 nm, and 777.5 nm, the electron densities and electron energy distribution functions determined using a Langmuir probe and multipole resonance probe as well as the state densities of the ?rst four excited states of argon measured with the branching fraction method and compared to tunable diode laser absorption spectroscopy. The in?uence of cascading and self absorption is included and the validity of the used cross sections and reaction rates is discussed in detail. The determined atomic oxygen state densities are discussed for their plausibility, sources of error, and compared to other measurements. Furthermore, the results of the model are analyzed to identify the application regimes of much simpler models, which could be used more easily for process control, e.g. actinometry.
关键词： absorption spectroscopy,atomic oxygen,probe measurements,collisional radiative model,optical emission spectroscopy
更新于2025-09-19 17:13:59
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Microsecond Resolved Infrared Spectroelectrochemistry Using Dual Frequency Comb IR Lasers
摘要： A dual infrared frequency comb spectrometer with heterodyne detection has been used to perform time resolved electrochemical attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). The measurement of the potential dependent desorption of a monolayer of a pyridine derivative (4-dimethylaminopyridine, DMAP) with time resolution as high as 4 μs was achieved without the use of step-scan interferometry. An analysis of the detection limit of the method as a function of both time resolution and measurement co-additions is provided and compared to step-scan experiments of an equivalent system. Dual frequency comb spectroscopy is shown to be highly amenable to time-resolved ATR-SEIRAS. Microsecond resolved spectra can be obtained with high spectral resolution and fractional monolayer detection limits in a total experimental duration that is two orders of magnitude less than the equivalent step-scan experiment.
关键词： 4-dimethyamino pyridine (DMAP),noise analysis,Dual frequency comb spectroscopy,time resolved spectroelectrochemistry,RC constant,attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS),detection limit
更新于2025-09-19 17:13:59
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A dominant factor of the cycloreversion reactivity of diarylethene derivatives as revealed by femtosecond time-resolved absorption spectroscopy
摘要： Dynamics of the cycloreversion reaction of a photochromic diarylethene derivative with a small ring-opening reaction yield (～1%) was investigated by using femtosecond transient absorption spectroscopy. The reaction rate constant and activation barrier on the reaction coordinate were quantitatively analyzed on the basis of the temperature and excitation wavelength dependencies of the reaction yield and excited state dynamics. From the comparison of the present results with those in a more reactive derivative, we concluded that a key factor regulating the overall reaction yield is the branching ratio at the conical intersection where the excited state population is split into the product and the initial reactant. The excitation wavelength dependence of the dynamics indicated that the geometrical relaxation and vibrational cooling proceed in a few picosecond time scale behind the cycloreversion process, and the vibrational excess energy assists the molecule to climb up the energy barrier.
关键词： vibrational cooling,diarylethene derivative,photochromic,femtosecond transient absorption spectroscopy,cycloreversion reaction
更新于2025-09-19 17:13:59
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Compact dual-gas sensor for simultaneous measurement of atmospheric methane, and water vapor using a 3.38?μm antimonide-distributed feedback laser diode
摘要： A simple, compact sensor involving a continuous-wave 3.38 mm distributed feedback laser in combination with a novel compact dense-pattern multipass cell was demonstrated for simultaneous measurement of atmospheric methane and water vapor. The calibration-free direct absorption spectroscopy approach was adopted for data generation and processing. Allan deviation analysis indicates that minimum detection limits (1s) of 11.0 ppb for CH4 and 100 ppm for H2O were achieved with a 1-s integration time at an optimum pressure of 50 Torr. Atmospheric environmental mixing ratios of these two gases were recorded and analyzed. This newly developed mid-infrared dual-gas sensor is very suitable for trace gas sensing in weight-limited unmanned aerial vehicle- or balloon-embedded field observations.
关键词： Multipass cell,Laser sensors,Water vapor,Distributed feedback laser,Laser absorption spectroscopy,Methane
更新于2025-09-19 17:13:59
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Internal Atomic-Scale Structure Determination and Band Alignment of IIa??VI Quantum Dot Heterostructures
摘要： This work shows that ZnTe/CdSe core/shell quantum dots synthesized by a standard literature procedure in actuality have an alloyed CdxZn1?xTe core. We employ X-ray absorption spectroscopy (XAS) at all four K-shell ionization edges (Zn, Te, Cd, and Se) and perform global ?tting analysis to extract the ?rst-shell bond distances. We combine our XAS results with transmission electron microscopy (TEM) sizing and elemental analyses, which allows us to propose models of the internal particle structure. Our multimodal characterization approach con?rms (1) the presence of Cd?Te bonds, (2) cation alloying in the particle core (and the absence of anion alloying), and (3) a patchy pure-phase CdSe shell. We synthesize particles of di?erent shell thicknesses and performed synthetic control studies that allowed us to discard a ZnTe/CdTe/CdSe core/shell/shell structure and con?rm the alloyed core/shell structure. Our structural analysis is extended with electronic band structure calculations and UV/vis absorption spectroscopy, demonstrating that the alloyed CdxZn1?xTe/CdSe core/shell quantum dots exhibit a direct band gap, di?erent from the predicted type II band alignment of the intended ZnTe/CdSe core/shell quantum dots. This study highlights the challenges with synthesizing II?VI quantum dot heterostructures and the power of XAS for understanding the internal structure of heterogeneous nanoparticles.
关键词： X-ray absorption spectroscopy,alloyed core,core/shell,band alignment,quantum dots
更新于2025-09-19 17:13:59
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InGaAs Membrane Waveguide: A Promising Platform for Monolithic Integrated Mid-Infrared Optical Gas Sensor
摘要： Mid-infrared (mid-IR) absorption spectroscopy based on integrated photonic circuits has shown great promise in trace-gas sensing applications in which the mid-IR radiation directly interacts with the targeted analyte. In this paper, considering monolithic integrated circuits with quantum cascade lasers (QCLs) and quantum cascade detectors (QCDs), the InGaAs-InP platform is chosen to fabricate passive waveguide gas-sensing devices. Fully suspended InGaAs waveguide devices with holey photonic crystal waveguides (HPCWs) and sub-wavelength grating cladding waveguides (SWWs) are designed and fabricated for mid-infrared sensing at λ=6.15μm in the low index contrast InGaAs-InP platform. We experimentally detect 5 ppm ammonia with a 1 mm long suspended HPCW and separately with a 3 mm long suspended SWW, with propagation losses of 39.1 dB/cm and 4.1 dB/cm, respectively. Furthermore, based on the Beer-Lambert infrared absorption law and the experimental results of discrete components, we estimated the minimum detectable gas concentration of 84 ppb from a QCL/QCD integrated SWW sensor. To the best of our knowledge, this is the first demonstration of suspended InGaAs membrane waveguides in the InGaAs-InP platform at such a long wavelength with gas sensing results. Also, this result emphasizes the advantage of SWWs to reduce the total transmission loss and the size of the fully integrated device’s footprint by virtue of its low propagation loss and TM mode compatibility in comparison to HPCWs. This study enables the possibility of monolithic integration of quantum cascade devices with TM-polarized characteristics and passive waveguide sensing devices for on-chip mid-IR absorption spectroscopy.
关键词： sub-wavelength waveguides,gas sensing,absorption spectroscopy,photonic crystal waveguides,mid-infrared,photonics integrated circuits,quantum cascade devices,parts-per-billion
更新于2025-09-19 17:13:59