Effects of Saturation on Laser-Induced Fluorescence Measurements of Population and Polarization

Altkorn, R

doi:10.1146/annurev.physchem.35.1.265

Cited by 119 publications

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“…As a result, the LIF intensities measured on OH A-X (1,0) Q 1 and P 1 lines can be directly related to the relative population of the OH X 2 Π 3/2 (v = 0, N) rotational levels utilizing a degeneracy term, rather than the Honl−London factors required in the unsaturated case. 36,51 (We were unable to eliminate a small contribution from overlapping satellite lines.) The nascent OH X 2 Π 3/2 (v = 0, N) rotational distribution obtained by probing A-X (1,0) Q 1 and P 1 lines following syn-CH 3 CHOO ν 2 excitation is shown in Figure 6; a similar distribution is observed upon ν 3 excitation.…”

Section: The Journal Of Physical Chemistry Amentioning

confidence: 99%

CH Stretch Activation of CH₃CHOO: Deep Tunneling to Hydroxyl Radical Products

et al. 2019

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Alkene ozonolysis, an important source of hydroxyl (OH) radicals in the Earth's troposphere, proceeds through unimolecular decay of Criegee intermediates. In this work, infrared activation of the methyl-substituted Criegee intermediate, syn-CH 3 CHOO, in the CH stretch fundamental region (2850−3150 cm −1 ) is shown to result in unimolecular decay to OH radical products. These excitation energies correspond to only half of the transition state barrier height, and thus the resultant 1,4 H atom transfer that leads to OH products occurs exclusively by quantum mechanical tunneling. Infrared action spectra recorded with UV laser-induced fluorescence detection of the OH products reveal the four CH stretch fundamentals and CO stretch overtone predicted to have strong transition strength. The vibrational band origins, relative intensities, and transition types derived from rotational band contour analyses are in good accord with theory. Distinctly different Lorentzian line broadening of the observed features is attributed to mode-specific anharmonic couplings predicted theoretically between spectroscopically bright and nearby dark states. The measured OH product state distribution shows a strong λ-doublet preference arising from pπ orbital alignment, which is indicative of the vinyl hydroperoxide intermediate along the reaction pathway. The unimolecular decay of syn-CH 3 CHOO at ca. 3000 cm −1 is predicted to be quite slow (ca. 10 5 s −1 ) using statistical Rice-Ramsperger-Kassel-Marcus theory with tunneling and much slower than observed at higher energies.

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Section: The Journal Of Physical Chemistry Amentioning

confidence: 99%

CH Stretch Activation of CH₃CHOO: Deep Tunneling to Hydroxyl Radical Products

et al. 2019

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“…At low probe laser powers, the fluorescence signal is linearly related to the laser power, and therefore the concentration of the absorbing species can be obtained 13 . As laser power is increased, upper level entrancement is eventually limited.…”

Section: Saturation and Non-saturation Regimesmentioning

confidence: 99%

Planar Laser Induced Fluorescence Mapping of a Carbon Laser Produced Plasma

Dorst¹,

Constantin²,

Schaeffer³

et al. 2022

Preprint

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We present measurements of ion velocity distribution profiles obtained by laser induced fluorescence (LIF) on an explosive laser produced plasma (LPP). The spatio-temporal evolution of the resulting carbon ion velocity distribution was mapped by scanning through the Doppler-shifted absorption wavelengths using a tunable, diode-pumped laser. The acquisition of this data was facilitated by the high repetition rate capability of the ablation laser (1 Hz) which allowed the accumulation of thousand of laser shots in short experimental times. By varying the intensity of the LIF beam, we were able to explore the effects of fluorescence power against laser irradiance in the context of evaluating the saturation versus the non-saturation regime. The small beam size of the LIF beam led to high spatial resolution of the measurement compared to other ion velocity distribution measurement techniques, while the fast-gated operation mode of the camera detector enabled the measurement of the relevant electron transitions.

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“…The alternative approach is to use a semi-classical rate equation analysis (72) . The latter procedure is easier to conceptualise and solve mathematically, but has a limited range of validity and may omit possible coherence effects (73) . The theory presented in this review is based on the semi-classical approach.…”

Section: Future Directionsmentioning

confidence: 99%

Optical imaging techniques for hypersonic impulse facilities

2007

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The application of optical imaging techniques to hypersonic facilities is discussed and examples of experimental measurements are provided. Traditional Schlieren and shadowgraph techniques still remain as inexpensive and easy to use flow visualisation techniques. With the advent of faster cameras, these methods are becoming increasingly important for time-resolved high-speed imaging. Interferometry’s quantitative nature is regularly used to obtain density information about hypersonic flows. Recent developments have seen an extension of the types of flows that can be imaged and the measurement of other flow parameters such as ionisation level. Planar laser induced fluorescence has been used to visualise complex flows and to measure such quantities as temperature and velocity. Future directions for optical imaging are discussed.

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Effects of Saturation on Laser-Induced Fluorescence Measurements of Population and Polarization

Cited by 119 publications

References 0 publications

CH Stretch Activation of CH₃CHOO: Deep Tunneling to Hydroxyl Radical Products

CH Stretch Activation of CH₃CHOO: Deep Tunneling to Hydroxyl Radical Products

Planar Laser Induced Fluorescence Mapping of a Carbon Laser Produced Plasma

Optical imaging techniques for hypersonic impulse facilities

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Effects of Saturation on Laser-Induced Fluorescence Measurements of Population and Polarization

Cited by 119 publications

References 0 publications

CH Stretch Activation of CH3CHOO: Deep Tunneling to Hydroxyl Radical Products

CH Stretch Activation of CH3CHOO: Deep Tunneling to Hydroxyl Radical Products

Planar Laser Induced Fluorescence Mapping of a Carbon Laser Produced Plasma

Optical imaging techniques for hypersonic impulse facilities

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CH Stretch Activation of CH₃CHOO: Deep Tunneling to Hydroxyl Radical Products

CH Stretch Activation of CH₃CHOO: Deep Tunneling to Hydroxyl Radical Products