Showing papers on "Fourier transform spectroscopy published in 2019"

Mid-infrared feed-forward dual-comb spectroscopy.

Abstract: Mid-infrared high-resolution spectroscopy has proven an invaluable tool for the study of the structure and dynamics of molecules in the gas phase. The advent of frequency combs advances the frontiers of precise molecular spectroscopy. Here we demonstrate, in the important 3-µm spectral region of the fundamental CH stretch in molecules, dual-comb spectroscopy with experimental coherence times between the combs that exceed half an hour. Mid-infrared Fourier transform spectroscopy using two frequency combs with self-calibration of the frequency scale, negligible contribution of the instrumental line shape to the spectral profiles, high signal-to-noise ratio, and broad spectral bandwidth opens up opportunities for precision spectroscopy of small molecules. Highly multiplexed metrology of line shapes may be envisioned.

Amine-assisted synthesis of FeWO4 nanorodg-C3N4 for enhanced visible light-driven Z-scheme photocatalysis

Abstract: Highly crystalline FeWO4 nanorods (FWO NRs) were prepared using an amine in a hydrothermal reaction. A photocatalyst active to visible light was designed by preparing 5FWO/g-CN heterostructures via in-situ hydrothermal methods. Fabricated heterostructures were analyzed using X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), BET measurements, transmission electron microscopy (TEM), X-ray photoelectron microscopy (XPS), and Fourier transform spectroscopy (FTIR). The photocatalytic activity toward the degradation of salicylic acid (SA) was investigated under visible light irradiation. The active species trapping experiments showed that the holes, as well as the electrons, exhibited an obvious influence on the photocatalytic degradation process. Examinations of the mechanism showed that the enhanced photocatalytic activity was mainly ascribed to reduced recombination rate and band gap broadening in a Z-scheme mechanism, which enhance the efficient transfer and the oxidation potential of the holes.

Influence of ultraviolet radiation on polymethylmethacrylate (PMMA)

Abstract: Polymethylmethacrylate (PMMA) was irradiated (360–811 h) in a UV-B accelerated aging chamber at room temperature and oxidizing atmosphere. The macromolecular changes attributed to the radiation were investigated by means of tests such as: traction test, percent cross-linking, thermogravimetric analysis (TGA), Fourier transform spectroscopy (FTIR) and ultraviolet visible spectroscopy (UV–Vis). Scanning electron microscopy (SEM) analysis was used to evaluate the influence of radiation on PMMA fracture behavior. The results indicate that changes occurred due to UV-B radiation, such as chain scission and color change, which may lead to a decrease in resistance. The mechanical properties curves showed a similar pattern for the irradiated samples, which are confirmed by the fragile fracture surface identified.

Mid-IR Spectroscopic Sensing

Abstract: Advances in mid-IR light sources and spectrometers are spurring development of fast, powerful instruments to explore a range of scientific, industrial and biomedical problems.

On-chip Fourier transform spectrometer on silicon-on-sapphire

Abstract: We designed and experimentally demonstrated an on-chip Fourier transform spectrometer on silicon-on-sapphire. The spectrometer comprises an array of twelve Mach–Zehnder interferometers (MZIs) with linearly increasing optical path delays between MZI arms. The propagation loss of 5.2 dB/cm has been experimentally observed for the strip waveguides. The retrieval of an optical spectrum is demonstrated with an inter-band cascade laser centered at 3.3 μm. The resolution is better than 10 cm−1.

Substrate-induced electronic localization in monolayer MoS 2 measured via terahertz spectroscopy

Abstract: We study terahertz (THz) optoelectronic properties of monolayer (ML) MoS2 placed on different substrates such as SiO2/Si, sapphire, and quartz. Through the measurements of THz Fourier transform spectroscopy (2.5–6.5 THz) and THz time-domain spectroscopy (TDS, 0.2–1.2 THz), we find that the real part of optical conductivity increases for ML MoS2 on SiO2/Si and sapphire substrates and decreases for it on quartz with increasing radiation frequency. It is shown that the complex optical conductivity for ML MoS2, obtained from THz TDS measurements, can fit very well to the Drude–Smith formula. Thus, the dependence of optical conductivity of ML MoS2 on different substrates can be understood via a mechanism of electronic localization, and the electron density, relaxation time, and localization factor of the sample can be determined optically. Furthermore, we examine the influence of temperature on these key parameters in ML MoS2 on different substrates. The results obtained from this Letter indicate that THz spectroscopy is a very powerful tool in studying and characterizing ML MoS2-based electronic systems, especially in examining the electronic localization effect which cannot be directly measured in conventional electrical transport experiment. This Letter is relevant to an in-depth understanding of the optoelectronic properties of ML MoS2 and of the proximity effect induced by different substrates.

Comb-resolved spectroscopy with immersion grating in long-wave infrared

Abstract: We have developed a dispersive spectrometer by using a compact immersion grating for direct frequency comb spectroscopy in the long-wave infrared region of 8-10 μm for the first time. A frequency resolution of 460 MHz is achieved, which is the highest reported in this wavelength region with a dispersive spectrometer. We also demonstrate individual comb mode-resolved imaging by cavity filtering and apply this to obtain spectra of both simple and complex molecular spectra. These results indicate that the immersion grating spectrometer offers the next advancement for sensitive, high-resolution spectroscopy of transient and large/complex molecules when combined with cavity enhancement and cooling techniques.

Background-free broadband absorption spectroscopy based on interferometric suppression with a sign-inverted waveform

Abstract: Background-free methods have potentially superior detection sensitivity because of their ability to take advantage of the full laser power; they are therefore attractive to spectroscopists. We implement background-free Fourier transform spectroscopy based on coherent suppression of the background using an interferometer, whereby the central peak of the interferogram is suppressed without losing molecular absorption signatures. This results in the appearance of peaks rather than dips in the measured spectrum. The technique can be used with a variety of broadband spectroscopies and features advantages such as a reduction in the required detector dynamic range, the capability to perform quantitative measurements, and strongly enhanced sensitivity down to the quantum limit. We validated our method experimentally by performing mid-infrared dual-comb spectroscopy with a mixture of multiple molecular species over a broad wavelength range of 3–5 μm.

Application of modulation excitation-phase sensitive detection-DRIFTS for in situ/operando characterization of heterogeneous catalysts

Abstract: This work describes the application of in situ/operando modulation excitation-phase sensitive detection-diffuse reflectance Fourier transform spectroscopy (ME-PSD-DRIFTS) for the characterization of heterogeneous catalysts. ME was enabled using a low void-volume diffuse reflectance cell which allowed rapid gas exchange (gas residence times <2 s) and by periodic feed concentration changes to the reaction cell by a simple switching valve system that provided quasi-square shaped modulation. PSD analysis of a relatively large data set of rapid scan spectra over many periodic cycles was done via a discrete Fourier transform (DFT)/frequency filtering/inverse discrete Fourier transform (IDFT) procedure. A general description of the ME-PSD principle, mathematical framework, guidelines for planning, running, and interpreting results was provided while focusing on ME-PSD-DRIFTS. Aspects such as the modulation frequency and amplitude, modulation waveform, sampling rate, in situ cell residence time, and limitations and future opportunities for ME-PSD-DRIFTS were also discussed. The proposed DFT/IDFT methodology uncovered the use of frequency magnitude plots for the evaluation of spectra baseline shifts, signal response to modulation, the response waveform type, noise, and signal decay/growth. Additionally, ethanol dehydration on γ-Al2O3 was presented as an example of application of the ME-PSD-DRIFTS methodology.

On-chip Fourier transform spectrometers by dual-polarized detection

Abstract: Chip-scale Fourier transform spectrometers (FTSs) have recently emerged for inexpensive, high-resolution spectroscopic applications. In particular, spatial-heterodyne FTSs (SH-FTSs) have drawn considerable attention with a simple and stable configuration based on an array of Mach–Zehnder interferometers (MZIs) with linearly increased optical path differences. There is a significant trade-off between spectral performance and the MZI number. In this work, we propose a dual-polarized SH-FTS, detecting both fundamental transverse electric and transverse magnetic modes, on a silicon photonic chip. Our experimental results show that, compared to the conventional single-polarized design, the MZI number of the dual-polarized SH-FTS can be nearly halved for a smaller footprint with little compromise of spectral performance.

Infrared absorption cross sections of isobutane with hydrogen and nitrogen as broadening gases

Abstract: Infrared absorption spectra of isobutane (C4H10) were recorded in the CH stretching spectral region (2500–3280 cm−1) by high resolution Fourier transform spectroscopy (Bruker IFS 125 HR). These spectra were taken at temperatures and pressures appropriate for the gas giant planets Jupiter and Saturn, as well as for Saturn's moon Titan. Absorption cross sections were obtained for pure samples and with broadening gases relevant in those atmospheres, hydrogen and nitrogen, to further simulate the astronomical environments. Corrections to the cross sections were made using data from the Pacific Northwest National Laboratory (PNNL) infrared database.

CO2-broadening and shift coefficients of sulfur dioxide near 4 µm

Abstract: The absorption spectra of the mixture of SO2 and CO2 at different partial pressures of both gases have been recorded at room temperature in the 4 µm region using the Bruker IFS 125 HR FTIR spectrometer. The multispectrum fitting procedure has been applied to these spectra to recover the CO2-broadening and shift parameters of the sulfur dioxide spectral lines. The CO2 broadening and the pressure induced shift coefficients for 1422 and 116 lines of the ν1 + ν3 A-type band of 32S16O2 and 34S16O2, respectively, have been derived. Beside, these coefficients have been derived for 254 lines of the ν1 + ν2 + ν3 − ν2 hot band of 32S16O2. The rotational dependence of the values of these coefficients is discussed. The CO2 pressure induced shift coefficients for this molecule are published for the first time. The comparison of the obtained broadening coefficients to those published by other authors for one pure rotational line and for the lines of the ν1 B-type band is given.

Time-resolved continuous-filtering Vernier spectroscopy of H2O and OH radical in a flame.

Abstract: We use broadband near-infrared continuous-filtering Vernier spectroscopy (CF-VS) for time-resolved detection of H2O and OH radical in a premixed CH4/air flat flame. The CF-VS spectrometer is based ...

Broadband static Fourier transform mid-infrared spectrometer

Abstract: For applications where only moderate spectral resolution is required, static Fourier transform infrared spectrometers (sFTS) offer a comparatively cost-effective alternative to classical scanning instruments. In this paper, we present an sFTS based on a single-mirror interferometer using only standard optical components and an uncooled microbolometer array. Because the instrument features concave mirrors rather than lenses, dispersion effects can be minimized. This enables broadband operation in the mid-infrared range from 2800 cm−1 to 600 cm−1 at a spectral resolution of 12 cm−1. In addition, the design guarantees comparatively high light throughput and can potentially be designed for increased temperature stability. Alongside a simulation of the temperature- and wavenumber-dependent behavior of the system, we provide a proof of principle of the proposed design by means of experimental results.

Preparation and electrochemical characterization of Mo9O26 nanopowders for supercapacitors applications

Abstract: In this work, the role of different solvent in the synthesis of Mo9O 26 nanoparticles was examined through hydrothermal method at optimized experimental conditions. The precursor solutions consists of sodium molybdate salts was dissolved respectively in deionized water, ethanol and mixture of ethanol and deionized water in a separate beaker and labeled as RSF1, RSF2 and RSF3. The obtained Mo9O 26 nanoparticles were examined by employing fundamental studies such as X-ray diffraction (XRD), Raman Spectroscopy, Fourier Transform Spectroscopy (FTIR), and Photoluminescence (PL) analysis. The obtained XRD spectra revealed the formations of Mo9O 26 nanoparticles employing the sharp diffraction peak appeared at 26.5o corresponding to the lattice planes of (−2 0 5) belongs to the space group P 1 ¯ ( 2 ) . FESEM analysis discloses the different configuration of Mo9O 26 nanoparticles such as truncated nanorods, fine agglomerated nanorods and half edge hexagonal structure for different solvents. Further, the electrochemical studies have been carried out employing cyclic voltammetry (CV) and galvanstatic charging–discharging studies. From CV studies, the active material as electrode (RSF1) delivers the high specific capacitance value of 672 Fg−1 at the low scan rate of 10 mV. The high specific capacitance of 623 Fg−1 at a current density 0.5 Ag−1 demonstrated by RSF1 is primarily due to the interconnected truncated nanorods which enhances the charge storage capacity by nearly 2 fold when compared to RSF2 and RSF3.

Coherent two-dimensional Fourier transform spectroscopy using a 25 Tesla resistive magnet.

Abstract: We performed nonlinear optical two-dimensional Fourier transform spectroscopy measurements using an optical resistive high-field magnet on GaAs quantum wells. Magnetic fields up to 25 T can be achieved using the split helix resistive magnet. Two-dimensional spectroscopy measurements based on the coherent four-wave mixing signal require phase stability. Therefore, these measurements are difficult to perform in environments prone to mechanical vibrations. Large resistive magnets use extensive quantities of cooling water, which causes mechanical vibrations, making two-dimensional Fourier transform spectroscopy very challenging. Here, we report on the strategies we used to overcome these challenges and maintain the required phase-stability throughout the measurement. A self-contained portable platform was used to set up the experiments within the time frame provided by a user facility. Furthermore, this platform was floated above the optical table in order to isolate it from vibrations originating from the resistive magnet. Finally, we present two-dimensional Fourier transform spectra obtained from GaAs quantum wells at magnetic fields up to 25 T and demonstrate the utility of this technique in providing important details, which are obscured in one dimensional spectroscopy.

Precision spectroscopy and comprehensive analysis of perturbations in the A 1 ∏(v = 0) state of 13 C 18 O

Abstract: We have reinvestigated the A level of 13C18O using new high-resolution spectra obtained via multi-photon laser excitation as well as with synchrotron-based Fourier-transform absorption spectroscopy...

Spectral resolution enhanced static Fourier transform spectrometer based on a birefringent retarder array.

Abstract: The principle and experimental demonstration of a spectral resolution enhanced static Fourier transform spectrometer (SESFTS) is presented. The device, which is based on a birefringent retarder array and a Wollaston prism, offers significant advantages over previous static Fourier transform (FT) implementations. Specifically, its use of an ultra-compact common-path interference structure creates a simple and robust spectral resolution enhanced spectrometer while preserving their high throughput and wide free spectral range. The operation principle of the device is explained in detail with a design example with a spectral resolution of 7 cm-1, which is nearly two orders of magnitude higher than that of a conventional static FT spectrometer with a similar CCD detector. An experimental demonstration is performed by the measurement of a gas charge lamp and three diode laser sources with a SESFTS prototype working in 400-1000 nm with an approximate 25 cm-1 spectral resolution.

The N2 second positive (C3Πu → B3Πg) system reviewed: Improved data and analysis

Abstract: A new ro-vibrational analysis of the N2 C3Πu → B3Πg system is performed by high resolution Fourier transform spectroscopy in the visible-UV region. A spectral region between 20,000 and 50,000 cm − 1 was covered in this analysis, with a total of 41 bands observed and studied. As a result, new and improved molecular constants were deduced from the attribution of observed spectral lines. With the new constants, potential energy curves were calculated for both states using the IPA method and in possession of these new curves, the Franck-Condon factors and r-centroids were calculated. Strong rotational perturbations were observed, such as spectral line shift and intensity anomalies, notably at the vibrational levels v′ = 1 and 2 of the C3Πu electronic state.

Fourier transform plasmon resonance spectrometer using nanoslit-nanowire pair

Abstract: In this paper, we present a nanoscale Fourier transform spectrometer using a plasmonic interferometer consisting of a tilt subwavelength slit-nanowire pair on a metallic surface fabricated by the focused ion beam microfabrication technique. The incident broadband light strongly couples with the surface plasmons on the gold surface, and thus, surface plasmon polaritons (SPPs) are generated. The launched SPPs interfere with the incident light and generate high contrast interference fringes in the nanoslit. The transmitted SPPs through the metal nanoslit can decouple into free space and are collected by an objective in the far field. The spectroscopic information of the incidence light is obtained by fast Fourier transform of the fringe pattern of the SPPs. In our design, there is no need for a bulky dispersive spectrometer or dispersive optical elements. The dimension of the spectrometer is around 200 μm length. Our design is based on inherent coherence of the SPP waves propagating through the subwavelength metal nanoslit structures etched into an opaque gold film.

Synthesis of novel cone-shaped CaAl-LDH directly on aluminum alloy by a facile urea hydrolysis method

Abstract: The urea method is one of the unique approaches to synthesize highly crystalline-layered double hydroxides (LDHs). Herein, we synthesized calcium-based layered double hydroxide (CaAl–LDH) directly on Al AA6082 substrate by using the urea hydrolysis reaction, in an effort to obtain highly potential novel cone-shaped unique LDH structure. The as-prepared CaAl-LDH thin film is characterized by X-ray diffraction, Fourier transform spectroscopy, scanning electron microscopy, transmission electron microscopy and further investigated the thermal properties and electron impedance spectra behavior. That simple in situ synthetic approach will be helpful to design environmentally friendly CaAl-LDH thin films that can be further investigated for numerous potential applications like environmental science, catalysts and biomedical applications.

Two-photon excitation spectroscopy of 1,5–Diphenyl-1,3,5-hexatriene using phase modulation

Abstract: We have used two-photon Fourier transform spectroscopy to investigate the first singlet excited state (S1) of a prototypical polyene molecule 1,5—Diphenyl-1,3,5-hexatriene. As the S1 state in the polyenes is a one-photon forbidden transition, the structure of its vibrational levels cannot be studied using resonant linear excitation. Although this level is accessible with two-photon excitation, previous studies done by using wavelength tunable pulsed lasers did not have enough resolution to investigate the details of the vibrational levels. In Fourier transform spectroscopy, one uses a pair of laser beams to excite the sample. The measurements are done by varying the time delay between the pulses. The spectral resolution is given by the inverse of the maximum time delay rather than the spectral width of the pulses. We have used the method to investigate the vibrational levels of the S1 state. In our implementation, we have used phase modulation to carry out the measurements in the rotating frame, which requires less data points along the time delay thereby significantly reducing the measurement time.

Measurement and modeling of self-broadening coefficients of the ν3 and 2ν3-ν3 bands of methyl chloride

Abstract: High-resolution Fourier Transform spectra have been recorded at room temperature in the frequency region around 13 µm using a high-resolution Fourier transform spectrometer (Bruker IFS 125-HR). Transitions of both 12CH335Cl and 12CH337Cl isotopologues belonging to the P, Q and R branches of the ν3 and 2ν3-ν3 parallel bands have been analyzed to retrieve self-broadening coefficients using a multispectrum fitting procedure that allowed to fit simultaneously the whole set of the experimental spectra recorded at seven pressures of CH3Cl ranging from 1.02 to 10.24 mbar. Line positions were also derived using a wavenumber calibration performed by the frequencies of OCS transitions. About 2028 lines with 2 ≤ J ≤ 59 and 2 ≤ K ≤ 13 have been studied. The rotational J and K dependencies of the self-broadening coefficients have been clearly observed and modeled using a second-order empirical polynomial. The average accuracy of the line parameters has been estimated to be about 4 and 5% for the ν3 and 2ν3-ν3 bands, respectively. Using the Robert and Bonamy formalism with parabolic and exact trajectory models, these coefficients were calculated, showing the predominance of the dipole-dipole interaction. The J and K rotational dependencies are consistent with the measured data. The predicted values confirm that the use of the exact trajectory model does not improve the predicted linewidths for a molecule with a large dipole moment such as CH3Cl.

Improvement of spectral resolution by signal padding method in the spatially modulated Fourier transform spectrometer based on a Sagnac interferometer.

Abstract: We propose the signal padding method to solve the problem of low spectral resolution in the spatially modulated Fourier transform spectrometer. The required number of sampling data for the given optical path difference was calculated and applied to the experimental data. The spatially modulated Fourier transform spectrometer based on the Sagnac interferometer was fabricated and its maximum optical path difference was 8 mm. A one-dimensional detector of 512 pixels was used to measure the spectrum of a LED light source of 6451 cm−1 center wavenumber. The obtained spectral resolution in an experiment for 1 mm optical path difference was 271 cm−1; however, it could be drastically improved to 31 cm−1 when the signal padding method was applied to the sidelobes of the measured interferogram.

Hyperspectral imager for the mid-infrared spectral range using a single-mirror interferometer and a windowing method

Abstract: In this paper, we present a static imaging Fourier transform spectrometer (sIFTS) for the mid-infrared spectral range. The system employs imaging optics, a single-mirror interferometer, and an uncooled broadband microbolometer array. As the hyperspectral data cube is acquired using a windowing method, a comparatively high light throughput in a spectral range from 2600 cm−1 to 800 cm−1, respectively 3.8 µm to 13 µm is achieved. The spectral resolution is 12 cm−1, and the spatial resolution amounts to 16 lp/mm, corresponding to a resolution of 62.5 µm at a design wavelength of 10.6 µm. As the employed spectrometer, in contrast to scanning Fourier transform infrared (FTIR) spectrometers, contains no moving parts, the measurement rate is mainly limited by the detector read-out and is currently 25 Hz. After an evaluation of the spatial resolution by both simulations and experimental results, the spatially resolved transmission spectra of a sample containing different polymer films are recorded and compared to a laboratory FTIR spectrometer. Thereby, the acquired spectra show good agreement. As the system combines both a spectrometer with low internal light loss and a windowing technique allowing high etendue, the presented hyperspectral imager shows significant potential especially for the mid-infrared.

Investigation of structural, optical and morphological properties of InGaN/GaN structure

Abstract: In this study, InGaN/GaN structure is investigated in the temperature range of 300–500 °C with steps of 50 °C. InGaN/GaN multi-quantum well structure is deposited on c-orientated sapphire wafer by metal organic chemical vapour deposition method. All the parameters except for temperature kept constant during growth period. InGaN/GaN structures with different In content are investigated by XRD technique. Their structural, optical and morphological characteristics are determined by high resolution X-ray diffraction, Fourier transform spectroscopy (FTIR), photo luminescence (PL), transmission and atomic force microscopy (AFM). According to FTIR and PL spectra’s, it is noticed that band gap values coincide with blue region in the electromagnetic spectrum. As a result of transmission measurements it is seen that light is completely absorbed by the sample at approximately 390 nm. Using XRD technique, dislocation densities and strain are calculated. Full width at half maximum of the XRD peak values gained from X-ray diffraction are used in an alternative method called Williamson–Hall (W–H). Using W–H method, lateral and vertical crystal lengths and tilt angles are determined. Surface roughness parameters are investigated by AFM. Different properties of GaN and InGaN layers are compared as dependent on increasing temperature. According to AFM images it is seen that these structures have high surface roughness and large crystal size. All the results yielded from the mentioned methods are in good agreement with the previous works done by different authors.

Fourier-transform spectroscopy of the A2Πi − X2Σ+ system in CO+ and deperturbation analysis of the A2Πi(v = 0, 1) levels

Abstract: The A2Πi state of 12C16O+ has been reinvestigated using high-resolution, emission spectra obtained via Fourier-transform spectroscopy of the (0, 1), (0, 2), (1, 0) and (1, 1) bands of the Comet–Tail (A2Πi − X2Σ+) system with accuracy of up to 0.005 cm−1. The high temperature (900 K) of the emission discharge inside the hollow-cathode lamp permitted monitoring of high rotational quantum levels in A2Πi(v = 0, 1) up to J = 48.5. All these bands together with the X2Σ+ − X2Σ+(10, 1) and (10, 2) transitions deriving from a complex, spin-orbit, spin-electronic and L-uncoupling A2Π(v = 0) ∼ X2Σ+(v = 10) interaction as well as the B2Σ+ − X2Σ+(6, 10) frequency transitions from our previous study were taken into consideration. In total, 1849 spectral lines were included in the comprehensive deperturbation analysis. This fit leads to a much improved description in terms of deperturbed molecular constants and interaction parameters compared to the previous studies of the same energy region in CO+. Moreover, the ro-vibronic term values of the A2Πi(v = 0) level and its perturber X2Σ+(v = 10) were determined as well as Λ-doubling of A2Πi(v = 0,1), γ-doubling of X2Σ+(v = 10) and percentage 2Π character of these levels were considered in detail.

Spatial Distribution of Impurity Defect Centers in Fe-Doped Polycrystalline Zinc Selenide

Abstract: The spatial distribution of impurity defect centers in Fe-doped chemical vapor deposited (CVD) ZnSe has been studied by two-photon confocal microscopy and scanning Fourier transform spectroscopy using an IR microscope. It has been shown that, as a result of doping with Fe, CVD ZnSe contains regions hundreds of microns in size that are parallel to the doping plane and differ in luminescence characteristics. The characteristics of these regions have been shown to correlate with the concentration of optically active Fe. Our results can be interpreted in terms of a model that assumes codiffusion of Fe and two types of impurity defect centers. We have pointed out that the data obtained in this study should be taken into account in interpreting results on the photoluminescence of semiconductors doped via thermal diffusion.

Measurements of N2-broadening and -shifting parameters of the water vapor spectral lines in the 19,560–19,920 cm−1 region using FT-spectrometer with LED source

Abstract: The water vapor line broadening and shifting coefficients for about 91 strongest water vapor lines in the 19,560–19,920 cm−1 spectral region induced by nitrogen pressure are measured with a spectral resolution of 0.05 cm−1 at room temperature by a Fourier transform spectrometer using high luminance LED light source. A high signal-to-noise ratio (S/N ≈ 10 000) allows one to analyze the lines with intensities from 1.54 × 10−23 to 2.0 × 10−26 cm/molecule. The multi-spectrum fitting procedure was used to fit line broadening and shift parameters of the 5ν1+ν3, and 6ν1 bands using the Voigt, Speed dependent Voigt and HTP profiles. Line width and shift values are calculated using a semi-empirical approach extended by the use of empirical data to determine some fitting model parameters. The method was further developed by using anharmonic wavefunctions in the estimates of line profile parameters.