Phase measurements in the frequency domain photoacoustic spectroscopy of solids

Mandelis, Andreas; Teng, Yichao; Royce, B. S. H.

doi:10.1063/1.325823

Cited by 114 publications

(26 citation statements)

References 14 publications

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“…Similar to the fluorescence phase modulation frequency domain, PA phase measurements in the frequency domain are directly related to the sample lifetime. [36][37][38][39] In this work, a PA method is proposed to determine the intrinsic quantum yield of lanthanide complexes in the condensed state. Through the ratio of the fast-to-slow heat component, intrinsic quantum yields of europiumA C H T U N G T R E N N U N G (III)-containing metallomesogens as well as terbiumA C H T U N G T R E N N U N G (III) complexes are determined.…”

Section: Introductionmentioning

confidence: 99%

Listening to Lanthanide Complexes: Determination of the Intrinsic Luminescence Quantum Yield by Nonradiative Relaxation

Yang

Liu

et al. 2008

ChemPhysChem

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The photophysical properties of lanthanide complexes have been studied extensively; however, fundamental parameters such as the intrinsic quantum yield as well as radiative and nonradiative decay rates are difficult or even impossible to measure experimentally. Herein, a photoacoustic (PA) method is proposed to determine the intrinsic quantum yield of lanthanide complexes with lifetimes in the order of milliseconds. This method is used to determine the intrinsic quantum yields for europium(III)‐containing metallomesogens as well as terbium(III) complexes. The results show that the PA signal is sensitive to both the lifetime and the ratio of the fast‐to‐slow heat component of the samples. It is found that there is an efficient ligand sensitization and a moderate intrinsic quantum yield for the complexes. The intrinsic quantum yield of Eu3+ in the metallomesogens exhibits an obvious increase upon the isotropic liquid to smectic A transition. The proposed PA method is quite simple, and can contribute to a clearer understanding of the photophysical processes in luminescent lanthanide complexes.

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Section: Introductionmentioning

confidence: 99%

Listening to Lanthanide Complexes: Determination of the Intrinsic Luminescence Quantum Yield by Nonradiative Relaxation

Yang

Liu

et al. 2008

ChemPhysChem

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“…1 (uncorrected in-phase spectrum). However, according to previous work and theory, 15,30,31 the photoacoustic phase should shift to earlier (i.e., smaller) phase values as the absorption coefficient increases. This indicates that the computed phase spectra for the 400 Hz data set does not lie in the 0Њ to 90Њ quadrant.…”

Section: Methodsmentioning

confidence: 99%

“…A possible explanation for these features is the background signal from the photoacoustic chamber. A thin oxide layer on a high thermal conductivity metal surface, such as the chamber wall, generates a fast phase signal 30 that becomes a factor in spectral regions where the sample absorbance is low. Applying the same tests to the 25 Hz phase modulation data set showed that the true phase of the Teflon spectra fell between 0Њ and 90Њ, so no prior processing of the single beam spectra was required.…”

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confidence: 99%

Observation of Large Photoacoustic Signal Phase Changes during a Diffusion Process

2005

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The phase of the photoacoustic signal is known to be a sensitive and accurate means to investigate, both qualitatively and quantitatively, static multilayer heterogeneous systems. According to theory, the maximum phase delay for a very weakly absorbing homogeneous sample should be within 45° of a very strongly absorbing sample, while for heterogeneous samples the phase delay can be greater than 45°. Here we report the observation of photoacoustic phase delays greater than 350°by extending the use of step-scan phase modulation photoacoustic spectroscopy to study a non-repetitive dynamic system in situ, in real time. These large phase delays correspond to sampling several thermal diffusion lengths into the sample. The model system used in this study consisted of a hydrocarbon grease diffusing through a porous Teflon film. The progress of the diffusion was tracked by monitoring both the photoacoustic signal magnitude and the phase of the hydrocarbon grease after isolation from the Teflon film signal contributions at two different phase modulation frequencies. The phase of the photoacoustic signal is known to be a sensitive and accurate means to investigate, both qualitatively and quantitatively, static multilayer heterogeneous systems. According to theory, the maximum phase delay for a very weakly absorbing homogeneous sample should be within 45؇ of a very strongly absorbing sample, while for heterogeneous samples the phase delay can be greater than 45؇. Here we report the observation of photoacoustic phase delays greater than 350؇ by extending the use of step-scan phase modulation photoacoustic spectroscopy to study a non-repetitive dynamic system in situ, in real time. These large phase delays correspond to sampling several thermal diffusion lengths into the sample. The model system used in this study consisted of a hydrocarbon grease diffusing through a porous Teflon film. The progress of the diffusion was tracked by monitoring both the photoacoustic signal magnitude and the phase of the hydrocarbon grease after isolation from the Teflon film signal contributions at two different phase modulation frequencies. Keywords

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“…This frequency-dependent penetration depth has been utilized to reconstruct thermal diffusivity depth profiles from the frequency-domain surface temperature data. Even though much experimental work [1][2][3][4] and some theoretical models [2,5] have been published regarding discontinuously inhomogeneous solids, theoretical implementation of realistic models addressing the equally important, and frequently more common, problem of continuously inhomogeneous solids has been less fertile. The most general and rigorous approach to the inverse thermal-wave problem has been given by Vidberg et al [6].…”

Section: Introductionmentioning

confidence: 99%

Depth profilometry of near-surface inhomogeneities via laser-photothermal probing of the thermal diffusivity of condensed phases

Mandelis

Munidasa

1994

Int J Thermophys

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Several applications are presented of the Hamilton-Jacobi formulation of thermal-wave physics to the problem of laser photothermal depth profilometry of the thermophysical transport parameter Ithe thermal diffusivity) of inhomogeneous condensed phases (solids and liquidsJ with arbitrary, continuously varying thermal diffusivity profiles. A working general method for solving the inverse problem and obtaining arbitrary diffusivity depth profiles from the laser beam-intensity modulation frequency dependence of the photothermal signal lamplitude and phasel is described. Specific examples of profile reconstructions are presented, including magnetic field-induced thermophysical inhomogeneities in liquid crystals, laser processing inhomogeneities in steels and Zr-Nb alloys, and finally, evaluation of machining damage in metals. Whenever possible. profiles obtained photothermally are compared with those resulting from destructive methods, such as microhardness testing.

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Phase measurements in the frequency domain photoacoustic spectroscopy of solids

Cited by 114 publications

References 14 publications

Listening to Lanthanide Complexes: Determination of the Intrinsic Luminescence Quantum Yield by Nonradiative Relaxation

Listening to Lanthanide Complexes: Determination of the Intrinsic Luminescence Quantum Yield by Nonradiative Relaxation

Observation of Large Photoacoustic Signal Phase Changes during a Diffusion Process

Depth profilometry of near-surface inhomogeneities via laser-photothermal probing of the thermal diffusivity of condensed phases

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