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Yamaji M, Kazmierczak F, Marciniak B. Steady-state, one-, and two-color laser flash photolysis studies of alpha-bond cleavage of S-acyl-4-phenylthiophenols in solution. J Phys Chem A 2009; 113:12831-7. [PMID: 19824652 DOI: 10.1021/jp9074459] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Photochemical properties of alpha-cleavage of the C-S bond in excited states of p-biphenyl thioacetate and p-biphenyl thiobenzoate (Me-SBP and Ph-SBP) in solution are investigated using steady-state and laser flash photolyses in comparison with those of S-phenyl thiobenzoate, where the photo-Fries rearrangement was reported to be absent. Although Me-SBP and Ph-SBP decompose upon 254 nm photolysis in acetonitrile irrespective of the amount of the dissolved oxygen, no definite photoproducts due to the photo-Fries rearrangement were found. Laser flash photolysis (266 nm) of these molecules reveals the occurrence of the C-S bond cleavage in the excited state based on the observation of the formation of the biphenylylthiyl radical (BTR) in the transient absorption. Quantum yields (Phi(rad)) of the BTR formation were determined to be 0.20 and 0.15 for Me-SBP and Ph-SBP, respectively. Triplet sensitization of Ph-SBP using xanthone (XT) as a sensitizer shows that the lowest triplet (T(1)) state of Ph-SBP is dissociative for the C-S bond with an efficiency of >or.56. In contrast, triplet sensitization of Me-SBP using acetone as a sensitizer demonstrates the efficient formation of triplet Me-SBP, and the molar absorption coefficient of the triplet-triplet absorption was determined. No photochemical reactions are found in the T(1) state of Me-SBP. Upon 355 nm laser flash photolysis of the T(1) state of Me-SBP, the formation of BTR is confirmed in the transient absorption. This observation indicates the C-S bond cleavage in a highly excited triplet (T(n)) state of Me-SBP. The quantum yield (Phi(dec)) of the alpha-cleavage in the T(n) state of Me-SBP was determined to be 0.69. Photochemical features of Me-SBP and Ph-SBP are discussed from the viewpoint of the spin-multiplicity of the bond dissociative states.
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Affiliation(s)
- Minoru Yamaji
- Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan.
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Reaction Control in Synthetic Organic Photochemistry: Switching between [5+2] and [2+2] Modes of Cycloaddition. Angew Chem Int Ed Engl 2009; 48:8716-20. [DOI: 10.1002/anie.200904059] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Roscini C, Cubbage K, Berry M, Orr-Ewing A, Booker-Milburn K. Reaction Control in Synthetic Organic Photochemistry: Switching between [5+2] and [2+2] Modes of Cycloaddition. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200904059] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Arce VB, Bertolotti SG, Oliveira FJVE, Airoldi C, Gonzalez MC, Allegretti PE, Mártire DO. The use of molecular probes for the characterization of dispersions of functionalized silica nanoparticles. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2009; 73:54-60. [PMID: 19237312 DOI: 10.1016/j.saa.2009.01.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2008] [Revised: 12/30/2008] [Accepted: 01/20/2009] [Indexed: 05/27/2023]
Abstract
Butoxylated silica nanoparticles (BSN) were prepared by esterification of the silanol groups of fumed silica nanoparticles with butanol and characterized by 13C and 29Si NMR and thermogravimetry. The molecular probes benzophenone (BP) and safranine-T were used to investigate the BSN suspensions in water:acetonitrile. Laser flash-photolysis experiments at lambda(exc)=266 nm performed with BSN suspended in acetonitrile:aqueous phosphate buffer supported previous results of our group obtained by time-resolved phosphorescence experiments and showed that only free and adsorbed excited triplet states of BP and diphenylketyl radicals contribute to the signals. The UV-vis spectroscopic and photophysical properties of safranine-T are strongly solvent-dependent. Thus, the analysis of the emission spectra and fluorescence lifetimes yielded information on the localization of this probe molecule in suspensions of BSN and of the bare silica nanoparticles. The values of the equilibrium constant for the adsorption of the ground-state safranine-T on the particles were found to be (9.2+/-0.8)x10(4), (7.2+/-0.8)x10(5), and (3.0+/-0.1)x10(4) for the BSN in 1:1 acetonitrile:water, SiO2 in 1:1 acetonitrile:water, and SiO2 in acetonitrile, respectively.
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Affiliation(s)
- Valeria B Arce
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), LADECOR, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
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Yamaji M, Cai X, Sakamoto M, Fujitsuka M, Majima T. α-Bond Dissociation of p-Phenylbenzoyl Derivatives in the Higher Triplet Excited State Studied by Two-Color Two-Laser Flash Photolysis. J Phys Chem A 2009; 113:1696-703. [DOI: 10.1021/jp8098208] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Minoru Yamaji
- Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan, and The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Xichen Cai
- Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan, and The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Masanori Sakamoto
- Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan, and The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Mamoru Fujitsuka
- Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan, and The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Tetsuro Majima
- Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan, and The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, Osaka 567-0047, Japan
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Yamaji M, Cai X, Sakamoto M, Fujitsuka M, Majima T. Photodecomposition Profiles of β-Bond Cleavage of Phenylphenacyl Derivatives in the Higher Triplet Excited States during Stepwise Two-Color Two-Laser Flash Photolysis. J Phys Chem A 2008; 112:11306-11. [DOI: 10.1021/jp805593m] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Minoru Yamaji
- The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, Osaka 567-0047, Japan, and Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
| | - Xichen Cai
- The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, Osaka 567-0047, Japan, and Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
| | - Masanori Sakamoto
- The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, Osaka 567-0047, Japan, and Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
| | - Mamoru Fujitsuka
- The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, Osaka 567-0047, Japan, and Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
| | - Tetsuro Majima
- The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, Osaka 567-0047, Japan, and Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
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Roscini C, Davies D, Berry M, Orr-Ewing A, Booker-Milburn K. Product Selection through Photon Flux: Laser-Specific Lactone Synthesis. Angew Chem Int Ed Engl 2008; 47:2283-6. [DOI: 10.1002/anie.200704816] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Roscini C, Davies D, Berry M, Orr-Ewing A, Booker-Milburn K. Product Selection through Photon Flux: Laser-Specific Lactone Synthesis. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200704816] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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9
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Photochemical decomposition of amidobiphenyls in highly excited triplet states studied by stepwise two-color laser photolysis. J Photochem Photobiol A Chem 2008. [DOI: 10.1016/j.jphotochem.2007.07.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Yamaji M. Stepwise two-color laser photolysis studies of α-cleavage in highly excited triplet states of α-acyl-4-phenylphenols. Photochem Photobiol Sci 2008; 7:711-7. [DOI: 10.1039/b716810a] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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11
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Yamaji M, Kojima A, Tobita S. Stepwise Laser Photolysis Studies of β-Bond Cleavage in Highly Excited Triplet States of Biphenyl Derivatives Having C−O Bonds. J Phys Chem A 2007; 111:770-6. [PMID: 17266216 DOI: 10.1021/jp065782i] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Photochemical profiles of beta-bond dissociation in highly excited triplet states (Tn) of biphenyl derivatives having C-O bonds were investigated in solution, using stepwise laser photolysis techniques. The lowest triplet states (T1) were produced by triplet sensitization of acetone (Ac) upon 308-nm laser photolysis. The molar absorption coefficients of the T1 states were determined using triplet sensitization techniques. Any photochemical reactions were absent in the T1 states. Upon 355-nm laser flash photolysis of the T1 states, they underwent fragmentation, because of homolysis of the C-O bond in the Tn states from the observations of the transient absorption of the corresponding radicals. The quantum yields (Phidec) for the decomposition of the T1 states upon the second 355-nm laser excitation were determined. Based on the Phidec values and the bond dissociation energies (BDEs) for the C-O bond fission, the state energies (ERT) of the reactive highly excited triplet states (TR) were determined. It was revealed that (i) the Phidec was related to the energy difference (DeltaE) between the BDE and the ERT, and (ii) the rate (kdis) of beta-cleavage in the TR state was formulated as being simply proportional to DeltaE. The reaction mechanism for beta-bond cleavage in the TR states was discussed.
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Affiliation(s)
- Minoru Yamaji
- Department of Chemistry, Gunma University, Kiryu 376-8515, Japan.
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Vieira Ferreira LF, Ferreira Machado I, Da Silva JP, Branco TJF. Surface photochemistry: benzophenone as a probe for the study of silica and reversed-phase silica surfaces. Photochem Photobiol Sci 2006; 5:665-73. [PMID: 16820853 DOI: 10.1039/b600384b] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This work reports the use of benzophenone, a very well characterized probe, to study new hosts: two reversed-phase silicas. Laser-induced room temperature luminescence of argon purged solid powdered samples of benzophenone adsorbed onto the two different reversed-phase silicas, RP-18 and RP-8, revealed the existence of a low energy emission band in contrast with the benzophenone adsorbed on 60 A pore silica, where only triplet benzophenone emits. This low energy emission band was identified as the fluorescence of the ketyl radical of benzophenone, which is formed as the result of a hydrogen atom abstraction reaction of the triplet excited benzophenone from the alkyl groups of the surface of the reversed silicas. Such emission does not exist for benzophenone adsorbed onto 60 A pore silica. Room temperature phosphorescence was obtained in argon purged samples for all the surfaces under use. The decay times of the benzophenone emission vary greatly with the alkylation of the silica surface when compared with "normal" silica surface. A lifetime distributions analysis has shown that the shortest lifetimes for the benzophenone emission exist in the former case. Triplet-triplet absorption of benzophenone was detected in all cases and is the predominant absorption in the case of 60 A pore silica, while benzophenone ketyl radical formation occurs in the case of the reversed silicas. Diffuse reflectance laser flash photolysis and gas chromatography-mass spectrometry techniques provided complementary information, the former about transient species and the latter regarding the final products formed after laser irradiation, both at 266 nm or 355 nm. Product analysis and identification show that the degradation photoproducts are dependent on the excitation wavelength, the photochemistry being much more rich and complex in the 266 nm excitation case, where an alpha-cleavage reaction occurs. A detailed mechanistic analysis is proposed.
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Affiliation(s)
- L F Vieira Ferreira
- Centro de Química-Física Molecular-Complexo Interdisciplinar, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001, Lisboa, Portugal.
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Cai X, Sakamoto M, Fujitsuka M, Majima T. Higher Triplet Excited States of Benzophenones and Bimolecular Triplet Energy Transfer Measured by Using Nanosecond-Picosecond Two-Color/Two-Laser Flash Photolysis. Chemistry 2005; 11:6471-7. [PMID: 16078292 DOI: 10.1002/chem.200500463] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The lifetimes of benzophenone in the higher triplet excited state (BP(T(n))) and several BP derivatives in the T(n) states were measured directly to be tau(T(n))=37+/-7 ps and 20-33 ps, respectively, by using the nanosecond-picosecond (ns-ps) two-color/two-laser flash photolysis method. Based on the direct measurements of tau(T(n)) of BP(T(n)), the triplet energy transfer (TET) from BP(T(n)) to quenchers (Q), such as carbon tetrachloride (CCl4), benzene (Bz), and p-dichlorbenzene (DCB), was investigated. The fast TET from BP(T(n)) to Q can be attributed to the lifetime-dependent quenching process, according to the Ware theoretical model of the bimolecular energy transfer reaction. The contribution of the lifetime-dependent term on k(TET) was 27, 60, and 86% for CCl4, Bz, and DCB as the Q of BP(T(n)), respectively, indicating that the TET from BP(T(n)) to Q is influenced not only by tau(T(n)), but also by the size of Q.
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Affiliation(s)
- Xichen Cai
- Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
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Cai X, Sakamoto M, Yamaji M, Fujitsuka M, Majima T. C−O Bond Cleavage of Benzophenone Substituted by 4-CH2OR (R= C6H5 and CH3) with Stepwise Two-Photon Excitation. J Phys Chem A 2005; 109:5989-94. [PMID: 16833934 DOI: 10.1021/jp051703b] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The C-O bond cleavage from benzophenone substituted with 4-CH2OR (p-BPCH2OR, 1-3), such as p-phenoxymethylbenzophenone (1, R= C6H5) and p-methoxymethylbenzophenone (2, R= CH3), occurred by a stepwise two-photon excitation during two-color, two-laser flash photolysis. On the other hand, no C-O bond cleavage occurred from p-hydroxymethylbenzophenone (3, R = H). The first 355-nm laser excitation of 1-3 generates p-BPCH2OR in the lowest triplet excited state (T1) which has an absorption at 532 nm. When p-BPCH2OR(T1) is excited with the second 532-nm laser to p-BPCH2OR in the higher triplet excited state (T(n)), the C-O bond cleavage occurred within the laser flash duration of 5 ns. The quantum yields of the C-O bond cleavage during the second 532-nm laser irradiation were found to be 0.015 +/- 0.007 and 0.007 +/- 0.003 for 1 and 2, respectively. Although these values are low, the diminishing 1(T1) or 2(T1) was found to convert, in almost 100% yield, to phenoxyl (C6H5O*) and p-benzoylbenzyl (BPCH2*) radicals or methoxyl (CH3O*) and BPCH2* radicals, respectively. The T(n) excitation energy, the energy barrier along the potential surface between the T(n) states and product radicals, and delocalization of the T(n) state molecular orbital including BP and CH2OR (R = C6H5, CH3, H) moieties are important factors for the occurrence of the C-O bond cleavage. It is found that the C-O bond cleavage and production of free radicals, such as BPCH2*, C6H5O*, and CH3O*, can be performed by a stepwise two-photon excitation. The present study is an example in which the chemical reactions can be selectively initiated from the T(n) state but not from the S1 and T1 states.
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Affiliation(s)
- Xichen Cai
- The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
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Cai X, Hara M, Kawai K, Tojo S, Majima T. Sensitized reactions by benzophenones in the higher triplet excited state. Chem Phys Lett 2003. [DOI: 10.1016/s0009-2614(03)00164-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Suzuki T, Omori T, Ichimura T. Excited-State Reaction of Short-Lived 2-Methylbenzophenone Enols Studied by Stepwise Two-Color Excitation Time-Resolved Thermal Lensing Technique. J Phys Chem A 2000. [DOI: 10.1021/jp001464m] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Tadashi Suzuki
- Department of Chemistry and Materials Science, Tokyo Institute of Technology, Ohokayama, Meguro-ku, Tokyo 152-8551, Japan
| | - Takashi Omori
- Department of Chemistry and Materials Science, Tokyo Institute of Technology, Ohokayama, Meguro-ku, Tokyo 152-8551, Japan
| | - Teijiro Ichimura
- Department of Chemistry and Materials Science, Tokyo Institute of Technology, Ohokayama, Meguro-ku, Tokyo 152-8551, Japan
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Study of the photophysics and energy transfer of 9,10-diphenylanthracene in solution. J Photochem Photobiol A Chem 2000. [DOI: 10.1016/s1010-6030(00)00322-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Allonas X, Ley C, Bibaut C, Jacques P, Fouassier J. Investigation of the triplet quantum yield of thioxanthone by time-resolved thermal lens spectroscopy: solvent and population lens effects. Chem Phys Lett 2000. [DOI: 10.1016/s0009-2614(00)00462-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Dissociation of highly excited triplet benzophenone into phenyl radicals and carbon monoxide: determination of the reaction quantum yield and the heat of reaction by time-resolved thermal lensing technique. Chem Phys 1994. [DOI: 10.1016/0301-0104(93)e0397-e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Takatori Y, Suzuki T, Kajii Y, Shibuya K, Obi K. Highly excited triplet state dynamics of benzophenone studied by pump and probe time-resolved thermal lensing spectroscopy. Chem Phys 1993. [DOI: 10.1016/0301-0104(93)80085-n] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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