A procedure for the numerical calculation of photoacoustic signals is introduced. It based on finite element method and uses an expansion signal into acoustic eigenmodes measuring cell. Loss included by incorporation quality factors. Surface volume loss effects attributable to viscosity thermal conductivity are considered. The verified cylindrical cells with excellent accordance. application unconventional shape yields good agreement experimental data.

This study compares the performance of a quartz tuning fork (QTF) with highly sensitive ultrasound microphone in context acoustic measurements, applying substitution calibration method. QTF sensors are increasingly used for high-precision tasks due to their sensitivity and stability, while microphones still standard general measurements. The aim this is evaluate both technologies across several key metrics, including linearity response, sensitivity, noise characteristics, detection limit....

We use the technique of terahertz time-domain spectroscopy to experimentally and theoretically study absorption dispersion ammonia vapor. Our measurements show small deviations from rotation-inversion spectrum which originate transitions in ν2 hot band (NH3)2 dimer. investigate molecular tunneling apply our new response theory analyze inversion this molecule. The includes polar molecules an external electric field over duration a collision with time as control parameter, it unifies basic...

With 1.6 million deaths per year, lung cancer is one of the leading causes death worldwide. One reason for this high number absence a preventive medical examination method. Many diagnoses occur in late stage with low survival rate. An early detection could significantly decrease mortality. In recent decades, certain substances human breath have been linked to diseases. Different studies show that it possible distinguish between patients and healthy control group by analyzing volatile organic...

In the field of photoacoustic sensors, research has mainly been concentrating on investigation cylinder shaped cells. For cells, important acoustical properties can be obtained by analytical methods. recent years, cells with other shapes have come into focus. these cases, sound spectrum and quantities interest cannot means. Finite element tools, however, are well suited to deal unconventional geometries. this article we present results concerning eigenmodes T-shaped

Photoacoustic spectroscopy employs acoustic resonators for signal amplification. Resonators are usually closed, however, in some applications, open preferred. The opening deteriorates the photoacoustic hence reducing sensitivity of measurement. We present two new approaches simulating using finite element modelling. based on amplitude mode expansion model and viscothermal with modelled perfectly matched layers boundary method respectively. Additionally, performance is extended to ultrasound...

Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS) is a technique in which the sound wave detected by quartz tuning fork (QTF). It enables particularly high specificity with respect to excitation frequency and well known for an extraordinarily sensitive analysis of gaseous samples. We have developed first photoacoustic (PA) cell QEPAS on solid Periodic heating sample excited modulated light from interband cascade laser (ICL) infrared region. The represents half-open cylinder that exhibits...

T-cell resonators have been used lately for non-invasive blood glucose measurements photoacoustic spectroscopy on skin samples. A resonator has a significant role in determining the strength of measured signal and overall sensitivity sensor. Here we present results measurement such resonator. The is also modelled using amplitude mode expansion method, which based eigenmode introduction losses form loss factors. reproduced almost all calculated resonances from numerical models with fairly...

We report, to our knowledge, the first optical detection scheme for short-chained hydrocarbon isotopologues. The sensor system is based on photoacoustic spectroscopy (PAS). Two continuous wave, thermoelectrically cooled, distributed feedback interband cascade lasers (DFB-ICLs) with emission wavelengths around 3.33 and 3.38 μm, respectively, served as light sources. investigations comprised main stable carbon isotopologues of methane (12CH4, 13CH4), ethane (12CH3-12CH3, 13CH3-12CH3,...

A finite element model including plasma simulation is used to calculate the amplitude of acoustic resonances in HID lamps a 2D axisymmetric geometry. Simulation results are presented for different operation parameters and compared with experimental data.

To the best of our knowledge, we present first-time measurements absorption cross sections 13C ethane and propane isotopologues in spectral region around 3000 cm-1. The spectra 13C12CH6, 13C2H6 13C12C2H8 have been recorded at approximate room temperature atmospheric pressure for concentrations between 0.325% 0.750% nitrogen using an FTIR spectrometer with a resolution 0.5 For calibration purposes spectrum each obtained natural isotopologue sample were compared to respective from Pacific...

High intensity discharge lamps can experience flickering and even destruction when operated at high frequency alternating current. The cause of these problems has been identified as acoustic resonances inside the lamp's arc tube. Here, a finite element approach for calculation response function is described. developed model does not include plasma dynamics.

We evaluate the spectral resolution and detection thresholds achievable for a photoacoustic spectroscopy (PAS) system in broadband infrared wavelength region 3270 n m ≲ λ 3530 driven by continuous wave optical parametric oscillator (OPO) with P ¯ ≈ 1.26 W . The absorption spectra, I PAS ( i ) , diluted propane, ethane methane test gases at low concentrations c ∼ 100 ppm were measured ∼1350 discrete wavelengths spectra then compared to high cross section data, σ FTIR obtained Fourier...

Photoacoustic (PA) measurements with open resonators usually provide poor detection sensitivity due to signal leakage at the resonator opening. We have recently demonstrated three different approaches for modelling photoacoustic of resonators. In this work, one is applied optimization geometry T-shaped improved strength and thus sensitivity. The results from numerical show an increase in by a factor approximately 7.23. They are confirmed using methods other than experimental measurement....

The Mach–Zehnder intensity Modulator (MZM), named after Ludwig Mach and Zehnder, is based on the corresponding interferometer. It splits light into two counter-rotating partial beams, which are later recombined with a controlled phase difference. output of MZM depends difference interferometer paths. This usually adjusted by an electrical voltage applied to Phase Shifter (PS) placed in one arms. For applications wavelength changing, must be accordingly. We derived equations describing...

High detection selectivity is extremely important for gas analyzers in order to correctly identify the measured compound. Therefore, laser-based systems require a high optical resolution, which primarily depends on spectral linewidth of radiation source. This study examines effective (chirp) pulsed distributed feedback (DFB) quantum cascade laser (QCL) photoacoustic (PA) system. The influence QCL operating parameters pulse duration and current as well impact modulation technique are...

This paper presents a numerical model of high-pressure sodium (HPS) lamps, including acoustic streaming. The is implemented in COMSOL and based on the finite-element method using 2-D axisymmetric geometry. Moreover, revision concerning experimental resonance (AR) characterizations HPS lamps will be also provided. results presented this contribute to understanding AR phenomena help electronic ballast design methods for avoidance.

We applied a multivariate analysis (MVA) to spectroscopic data of gas mixtures in the mid-IR order calculate concentrations single components which exhibit strongly overlapping absorption spectra. This is common challenge broadband spectroscopy. Photoacoustic (PA) measurements different volatile organic compounds (VOCs) wavelength region 3250 nm 3550 served as exemplary detection technique. Partial least squares regression (PLS) was used from PA After calibration, PLS model able determine...