A photoconductivity study of trapped electrons in γ-irradiated hydrocarbon glasses at 77 K

Okabe, Naoto; Kimura, Toyoaki; Fueki, Kenji

doi:10.1139/v83-482

Cited by 9 publications

(11 citation statements)

References 14 publications

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“…Small artifacts of the TMPD cation subtraction are present at 1.9-2.2 eV. Spectra for 2MP, 3MP, and MCH have been previously reported, 39,46 and agree substantially with those reported here.…”

Section: Resultssupporting

confidence: 89%

Absorption Spectra of Trapped Electrons in Nonpolar Glasses: Oscillator Strengths and Threshold Behaviors

and

Lipsky

2001

J. Phys. Chem. A

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Trapped electrons were generated by photoionization of TMPD (N,N,N′,N′-tetramethylparaphenylenediamine) and the absorption spectra measured in 2-methylpentane (2MP), 3-methylpentane (3MP), cis-decalin (CD), methylcyclohexane (MCH), and deuterated methylcyclohexane(dMCH) glasses at 77 K. The low energy absorption fits the Wigner 3/2 power law for threshold photodetachment, consistent with a ground S state with binding energy of 0.48 ( 0.02 eV and a final continuum P state. For all solvents studied, the maximum absorption cross-section is located at ca. 0.7 eV with an extinction coefficient of 2.7 × 10 4 M -1 cm -1 (determined by comparison to TMPD cation). From the spectral distribution of the absorption (from 0.5 to 3.3 eV), experimental oscillator strengths were determined to be 0.65(2MP), 0.63(3MP), and 0.76(CD). Various local field corrections to these experimental oscillator strengths are discussed.

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Section: Resultssupporting

confidence: 89%

Absorption Spectra of Trapped Electrons in Nonpolar Glasses: Oscillator Strengths and Threshold Behaviors

and

Lipsky

2001

J. Phys. Chem. A

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“…When the ratio of the corresponding cross sections is plotted against the photon energy E , it appears that the quantum yield φ t of photodetrapping is a sigmoid function centered at E E bc = to the blue of the absorption maximum. 72,74,76 The constancy of φ t for E E bc > suggests that φ t ≈ 1. 72 The surprising aspect of these measurements is that the action spectra produced by different methods (absorption bleaching, 77,78 EPR, 79 conductivity, 72,74,76 and luminescence 77 ) are not the same.…”

Section: A Absorption Spectra and Photodetachment Cross Sectionsmentioning

confidence: 99%

“…72,74,76 The constancy of φ t for E E bc > suggests that φ t ≈ 1. 72 The surprising aspect of these measurements is that the action spectra produced by different methods (absorption bleaching, 77,78 EPR, 79 conductivity, 72,74,76 and luminescence 77 ) are not the same. 10 The similarity between the action spectra and absorption spectra was observed for some vitreous hydrocarbons (e.g., methylcyclohexane) 71 but not for others (e.g., 3-20.…”

Section: A Absorption Spectra and Photodetachment Cross Sectionsmentioning

confidence: 99%

“…concerning the electron spectra in the vitreous hydrocarbons: (i) that the entire spectrum is due to the bc transitions, 9,43,44,71 and (ii) that the bc transitions dominate only above a certain threshold energy E bc (ca. 1 eV); 10,[72][73][74] below this energy, both the bc and bb transitions may occur. The latter situation occurs for solvated electrons in the polar media, where the potential wells are deep.…”

Section: A Absorption Spectra and Photodetachment Cross Sectionsmentioning

confidence: 99%

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Photostimulated electron detrapping and the two-state model for electron transport in nonpolar liquids

Shkrob¹,

Sauer²

2005

The Journal of Chemical Physics

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In common nonpolar liquids, such as saturated hydrocarbons, there is a dynamic equilibrium between trapped (localized) and quasifree (extended) states of the excess electron (the two-state model). Using time-resolved dc conductivity, the effect of 1064 nm laser photoexcitation of trapped electrons on the charge transport has been observed in liquid n-hexane and methylcyclohexane. The light promotes the electron from the trap into the conduction band of the liquid. From the analysis of the two-pulse, two-color photoconductivity data, the residence time of the electrons in traps has been estimated as ca. 8.3 ps for n-hexane and ca. 13 ps for methylcyclohexane (at 295 K). The rate of detrapping decreases at lower temperature with an activation energy of ca. 200 meV (280-320 K); the lifetime-mobility product for quasifree electrons scales linearly with the temperature. We suggest that the properties of trapped electrons in hydrocarbon liquids can be well accounted for using the simple spherical cavity model. The estimated localization time of the quasifree electron is 20-50 fs; both time estimates are in agreement with the "quasiballistic" model. This localization time is significantly lower than the value of 310±100 fs obtained using time-domain terahertz (THz) spectroscopy 2.for the same system [E. Knoesel et al., J. Chem. Phys. 121, 394 (2004)]. We suggest that the THz signal originates from the oscillations of electron bubbles rather than the freeelectron plasma; vibrations of these bubbles may be responsible for the deviations from the Drude behavior observed below 0.4 THz. Various implications of these results are discussed.

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“…Concerning trapped electrons in nonpolar hydrocarbon glasses at 77 K, it is well known that the electron spin resonance (esr) spectra for those electrons show a singlet line with a line width of -4 G (1), that absorption maxima of optical absorption spectra are -1700 nm(l), and that photoconductivity maxima of photoconductivity spectra are -1000 nm (2). It is also known that electrons are efficiently trapped in glassy matrices but not in crystalline matrices.…”

Section: Introductionmentioning

confidence: 99%

A photoconductivity study in γ-irradiated polyethylene at 77 K

Kimura¹,

Ueda²,

Hirai³

1986

Can. J. Chem.

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TOYOAH KIMURA, YUTAKA UEDA, and YOHICHI HIRAI. Can. J. Chem. 64, 695 (1986).A photoconductivity study was made on y-irradiated low and high density polyethylene using 3-methylpentane, methylene chloride, and hexafluorobenzene as dopants. Electron spin resonance (esr) and optical absorption measurements were made together with photoconductivity. A study was also made for poly(4-methylpentene-1). The process of photocurrent generation is not ascribed totally to photodetrapping of trapped electrons in polyethylene; the process by photodetrapping of trapped electrons dominantly contributes to photocurrent generation in the ir region and may partly contribute in the visible region but not in the uv region. Another process for photocurrent generation other than photodetrapping of trapped electrons exists in the uv and perhaps partly in the visible region. We have tentatively ascribed this process to photodetachent of electrons from carbanions whch are formed by the reaction between radicals and electrons.TOYOAH KIMURA, YUTAKA UEDA et YOHICHI HIRAI. Can. J. Chem. 64, 695 (1986).On a effectut une Ctude de photoconductivitC sur des polyCthylknes de basse et de haute densitC, irradiCs aux rayons y et contenant les substances suivantes comme dopants: mtthyl-3 pentane, chlorure de mCthylkne et hexafluorobenzkne. En plus de la photoconductivitt5, on a aussi effectut des mesures de rpe et d'absorption. On a aussi CtudiC le poly(mCthy1-4-pentkne-1). On n'attribue pas tout le processus de la gCnCration du photocurant au photodCpiCgeage des Clectrons piCgCs dans le polyCthylkne; ce processus de photodCpiCgeage des Clectrons piCgCs contribue d'une faqon dominante a la gCnCration du photocourant dans le region de I'ir et peut aussi contribuer en partie dans la rCgion du visible, mais pas dans la region de l'uv. En plus du photodCpiCgeage des Clectrons piCgCs, un autre processus de gtneration de photocourant existe dans l'uv et peut-Ctre aussi dans le visible. Sur une base priliminaire, on a attribuC ce processus au photodttachement des Clectrons des carbanions qui se foment par la rCaction des radicaux et des Clectrons.[Traduit par la revue]

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A photoconductivity study of trapped electrons in γ-irradiated hydrocarbon glasses at 77 K

Cited by 9 publications

References 14 publications

Absorption Spectra of Trapped Electrons in Nonpolar Glasses: Oscillator Strengths and Threshold Behaviors

Absorption Spectra of Trapped Electrons in Nonpolar Glasses: Oscillator Strengths and Threshold Behaviors

Photostimulated electron detrapping and the two-state model for electron transport in nonpolar liquids

A photoconductivity study in γ-irradiated polyethylene at 77 K

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