Picosecond photodissociation of dibenzyl ketone

Arbour, C.; Atkinson, Gordon

doi:10.1016/0009-2614(89)87525-6

Cited by 23 publications

(14 citation statements)

References 9 publications

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“…The excitation of dibenzyl ketone leads to very rapid production of two PhCH 2 • radicals as a result of the initial α-cleavage and rapid decarbonylation of the phenylacetyl radical: − In acetonitrile, Φ esc was found to be 0.85 ± 0.17. This estimate is within reasonable agreement of the previously reported value of 0.71 ± 0.11 …”

Section: Resultsmentioning

confidence: 99%

Quenching of Singlet Oxygen by Oxygen- and Sulfur-Centered Radicals: Evidence for Energy Transfer to Peroxyl Radicals in Solution

et al. 1998

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Quenching of singlet oxygen luminescence at 1.27 µm by PhS • , PhSO • , and peroxyl radicals PhOO • , t-BuOO • , PhCH 2 OO • , Ph 2 CHOO • , and Ph 3 COO • was studied in liquid solution. The quantum yields of decomposition of different initiators which lead to the formation of free radicals were measured by using nanosecond transient absorption. This allowed determination of singlet oxygen O 2 ( 1 ∆ g ) quenching rate constants by the radicals. They are <2 × 10 8 M -1 s -1 for the sulfur-centered radicals and (2-7) × 10 9 M -1 s -1 for peroxyl radicals in acetonitrile. The rapid quenching is attributed to energy transfer quenching by the peroxyls, which have an n f π* transition leading to a low-lying 2 A′ state above their 2 A′′ ground state. PhSO • is shown computationally not to have such a low-lying 2 A′ state. There may be a very low-lying 2 B 1 state, for PhS • , but it is apparently not an efficient acceptor of electronic energy from O 2 ( 1 ∆ g ).

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Section: Resultsmentioning

confidence: 99%

Quenching of Singlet Oxygen by Oxygen- and Sulfur-Centered Radicals: Evidence for Energy Transfer to Peroxyl Radicals in Solution

et al. 1998

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“…The instrumentation used to obtain PTR3 data ( Fig. 2) has been described in detail elsewhere (Atkinson et ul., 1989;Arbour and Atkinson, 1989). Briefly, the fundamental output of a mode-locked, Qswitched Nd:YAG laser (Quantronix model 416) is separately tripled and doubled in order to pump two synchronously-pumped dye lasers (Coherent model 740).…”

Section: Methodsmentioning

confidence: 99%

“…Picosecond transient absorption (PTA) data also are obtained on the same sample using the same laser instrumentation and with methods described elsewhere Arbour and Atkinson, 1989). The PTA of the excited-state p-carotene over the 560-590 nm range is measured by spatially separating the probe beam from the pump beam after they both exit the sample jet.…”

Section: Methodsmentioning

confidence: 99%

RESONANCE RAMAN SPECTRUM OF THE EXCITED 21A_g STATE OF ß‐CAROTENE

Noguchi¹,

Kolaczkowski²,

Arbour³

et al. 1989

Photochem & Photobiology

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Abstract— Resonance Raman (RR) bands assignable to the 21Ag excited state of ß‐carotene are recorded using picosecond time‐resolved resonance Raman (PTR3) spectroscopy. The RR spectrum contains bands in both the C‐C (1204 cm−1, 1243 cm−1, and 1282 cm−1) and C=C (1777 cm−1) stretching regions. The time‐dependent intensities of these RR features, measured with ˜ 30 ps. resolution, are found (i) to closely correlate with picosecond transient absorption (PTA) data recorded at 575 nm on the same sample and (ii) inversely correlate with the time‐dependent intensities of RR bands assigned to the 11Ag ground state. Both of these observations support the assignment of these four RR features to the 21Ag excited state. These results remove uncertainties associated with earlier experiments in which excited‐state RR scattering from (3‐carotene was not observed in spite of predicted trends emanating from studies of shorter polyene compounds. The observed C=C band position also agrees with a recent report of this feature.

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“…In the case of DBK and DPP, for which the possibility of upper singlet cleavage is most likely, we found that the fluorescence excitation spectra are identical to that for acetone, for which there (2) rate-limiting ISC to Ti occurs followed by extremely rapid (<100 ps) dissociation. 47 The first option is in conflict with nearly all published mechanistic experimental data (quenching experi-ments23•24 and all magnetic effect results-CIDNP, CIDEP, MIE, and mafnetic field effects2-5), which require a significant contribution of DBK triplet to the dissociation process. However, a small contribution of DBK photochemistry is quite possible and is not inconsistent with our data.…”

Section: Discussionmentioning

confidence: 99%

Wavelength effects in the photolysis of ketones: stereoisomerization and magnetic isotope carbon-13/carbon-12 separation; a probe for adiabatic versus diabatic trajectories during bond dissociation

Step¹,

Tarasov²,

Buchachenko³

et al. 1993

J. Phys. Chem.

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The I3C enrichment in the photolysis of three ketones, dibenzyl ketone (DBK), (S)-(+)-a-methyldeoxybenzoin (MDB), and d,l-2,4-diphenylpentan-3-one (DPP), along with the photostereoisomerization of the latter two From the simple paradigm of eq 1, the value P,, the probability of combination of a primary geminate pair, is a potentially useful and intuitive mechanistic parametcfl~~ which clearly represents the competition between the knit process and all other competing processes.When the primary geminate pair is created in a singlet state (IRP), the value of Pr is often close to unity and is relatively lacking in mechanistic information. On the other hand, when the primary geminate pair is produced in a triplet state ORP), the intersystem crossing step, )RP -'RP, requires a magnetic interaction and may ku" rate determining and, before the

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Picosecond photodissociation of dibenzyl ketone

Cited by 23 publications

References 9 publications

Quenching of Singlet Oxygen by Oxygen- and Sulfur-Centered Radicals: Evidence for Energy Transfer to Peroxyl Radicals in Solution

Quenching of Singlet Oxygen by Oxygen- and Sulfur-Centered Radicals: Evidence for Energy Transfer to Peroxyl Radicals in Solution

RESONANCE RAMAN SPECTRUM OF THE EXCITED 21A_g STATE OF ß‐CAROTENE

Wavelength effects in the photolysis of ketones: stereoisomerization and magnetic isotope carbon-13/carbon-12 separation; a probe for adiabatic versus diabatic trajectories during bond dissociation

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Picosecond photodissociation of dibenzyl ketone

Cited by 23 publications

References 9 publications

Quenching of Singlet Oxygen by Oxygen- and Sulfur-Centered Radicals: Evidence for Energy Transfer to Peroxyl Radicals in Solution

Quenching of Singlet Oxygen by Oxygen- and Sulfur-Centered Radicals: Evidence for Energy Transfer to Peroxyl Radicals in Solution

RESONANCE RAMAN SPECTRUM OF THE EXCITED 21Ag STATE OF ß‐CAROTENE

Wavelength effects in the photolysis of ketones: stereoisomerization and magnetic isotope carbon-13/carbon-12 separation; a probe for adiabatic versus diabatic trajectories during bond dissociation

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RESONANCE RAMAN SPECTRUM OF THE EXCITED 21A_g STATE OF ß‐CAROTENE