Laser Photochemistry Research Articles

UV laser photochemistry of pentaborane(9) at 193 nm: quantum yield of primary BH 3 formation and its subsequent chemistry

Excitation of B 5H 9 in the gas phase by ArF laser radiation at 193 nm causes primary dissociation into BH 3 plus B 4H 6. Rapid recombination probably leads to the reactive intermediate B 5H 7, which upon addition to B 5H 9 forms B 10H 14 and B 10H 16. B 6H 10 production as well as polymerization can be understood to proceed via the intermediate B 8H 12, which arises from the dimerization of B 4H 6 fragments.

Two-photon laser photochemistry of a coumarin laser dye

Abstract Irradiation of 7-dimethylamino-4-methylcoumarin (1), a commercially available laser dye, in ethanol solution with the focused output of an XeCl excimer laser at 308 nm resulted in the formation of yellow oligomeric material derived from the ethanol solvent. The efficiency of formation of the yellow material was shown to be dependent on the intensity of the laser light, indicating that the photochemistry involved absorption of two photons. The oligomeric material is proposed to be a substance which interferes with stimulated emission in coumarin dye lasers. In addition, acetaldehyde and several gaseous products, principally hydrogen and butane, were formed. A product resulting from the coupling of 1 with the ethanol solvent was also isolated and characterized. Excimer laser irradiation of 1 in methanol yielded formaldehyde, hydrogen and solvent oligomers, while irradiation of 1 in benzene resulted in the formation of a black precipitate. The non-oligomeric products are similar to those observed from the direct irradiation of the solvent in the vacuum-UV region. A mechanism is proposed for the observed photochemistry in which 1 absorbs, sequentially, two photons from the laser pulse, resulting in the formation of a highly excited state which then transfers energy to the solvent.

Laser Photochemistry and Hole Burning Spectroscopy in Polymers and Glasses: External Field Effects

Photochemical hole burning is a spectroscopic method based on site-selection via laser irradiation. It can be shown, that it yields a 103 to 104-fold increase in resolution if one deals with amorphous materials such as solid polymers. For various doped polymers (polyethylene, polystyrene, poly(methyl methacrylate), and poly(vinyl butyral)) we have made experiments under low electric field and strain field conditions. These experiments yield both, matrix parameters such as compressibilities and molecular parameters such as molecular dipole moment changes and polarizability changes. We will document, that the amorphous nature of the matrix breaks the molecular symmetry of the dopant molecules and gives rise to internal electric dipole moments or internal fields, which are absent in a periodic crystalline structure.

UV laser photochemistry: Evidence for “through-bond coupling” effects in the lifetimes of 2,2-dimethyl-1,3-cyclopentadiyl triplet diradicals.

The 2,2-dimethyl substituted 1,3-diradicals 5a-c possess significantly shorter triplet lifetimes (τ t) than the parent 1,3-cyclopentadiyl 3 , which is being rationalized on the basis of changes in the “through-bond” coupling and thus singlet-triplet energy splitting between the radical sites.

The infrared laser photochemistry of silane

The infrared laser photochemistry of silane

ChemInform Abstract: Preparative UV‐VIS Laser Photochemistry: Molecular Oxygen Trapping of the Paterno‐Büchi Triplet Diradicals Derived from 1,4‐Dioxene.

Abstract1,4‐Dioxen (I) addiert die Ketone (II) unter Laser‐Bestrahlung zu den Bicyclen (III).

Laser photochemistry of aromatic substituted cyclobutanes and cyclobutenes

The photochemical ring opening and ring cleavage reactions of 6b,8a-dihydrocyclobut[a]acenaphthylene (1) and two similar compounds are described. These reactions occur at room temperature only if the irradiating light intensity is greater than MW/cm 2, easily obtained with excimer and dye lasers. This is rationalized in terms of a consecutive two-photon absorption to reach higher-lying reactive states. The mechanism proposed for the reaction of 1 also describes the product distribution, which depends on irradiation parameters such as laser pulse length, wavelength, intensity, and oxygen content of the solvent.

UV/VIS Laser Photochemistry: Intermediary Formation of Diazoalkanes versus Direct S0,T1 Transitions in the Photolysis of Azoalkanes

UV/VIS Laser Photochemistry: Intermediary Formation of Diazoalkanes versus Direct S₀,T₁ Transitions in the Photolysis of Azoalkanes

ChemInform Abstract: High Power Laser Photochemistry. Production of Neutral Atomic and Small Molecular Fragments by UV Multiphoton Dissociation

Chemischer InformationsdienstVolume 17, Issue 16 Preparative Organic Chemistry ChemInform Abstract: High Power Laser Photochemistry. Production of Neutral Atomic and Small Molecular Fragments by UV Multiphoton Dissociation P. CHEN, P. CHENSearch for more papers by this authorJ. B. PALLIX, J. B. PALLIXSearch for more papers by this authorW. A. CHUPKA, W. A. CHUPKASearch for more papers by this authorS. D. COLSON, S. D. COLSONSearch for more papers by this author P. CHEN, P. CHENSearch for more papers by this authorJ. B. PALLIX, J. B. PALLIXSearch for more papers by this authorW. A. CHUPKA, W. A. CHUPKASearch for more papers by this authorS. D. COLSON, S. D. COLSONSearch for more papers by this author First published: April 22, 1986 https://doi.org/10.1002/chin.198616124AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue16April 22, 1986 RelatedInformation

UV laser photochemistry: triplet biradical trapping efficiencies and lifetimes

The trapping of triplet 1,3-cyclopentadiyl (1) and the triplet 1,4-biradical 2-(2-ethyl)cyclopent-2-enyl (2) with molecular oxygen has been studied quantitatively. The lifetime of 1 has been found to range between 720 and 900 ns and that of 2 between 53 and 94 ns depending on the solvent. The biradical 1 was found to be trapped in essentially quantitative yield with no indication of oxygen-catalyzed intersystem crossing. In contrast, 2 was found to be trapped in 54-79% yield with the residual biradical quenching being due to oxygen-catalyzed intersystem crossing. These and other biradical trapping data have been correlated with 1,3-biradical geometries and found to be in accord with Salem's rules for spin-orbit coupling in triplet biradicals. 28 references, 7 figures, 2 tables.

UV laser photochemistry and diborane at 193 nm: Quantum yield for BH 3 production

The quantum yield ø BH 3 for BH 3 production from ArF-laser-excited B 2H 6 was determined to be 2.00 ± 0.25 by trapping with PF 3. The former postulate of BH 3 as a chain carrier in ArF-laser-induced B 2H 6-D 2 exchange is confirmed.

Laser-induced processes in spectroscopy, isotope separation, and photochemistry

The use of stimulated quantum transitions in atoms and molecules for their resonant excitation is reviewed. The applications of this approach in laser spectroscopy, laser isotope separation, and laser photochemistry are briefly discussed.

High power laser photochemistry. Production of neutral atomic and small molecular fragments by UV multiphoton dissociation

Atomic carbon, Ch, CH2, and CH3, produced by UV multiphoton dissociation, have been detected by resonant MPI on picosecond and nanosecond time scales. Large yields of neutral fragments produced within the pulse width of the dissociation laser suggest that exceedingly rapid radiationless transitions must occur, suppressing ionization of the parent molecule.

Preparative UV-VIS laser photochemistry; molecular oxygen trapping of the Paterno-Büchi triplet diradicals derived from 1,4-dioxene.

Argon ion laser irradiation of CCl 4 solutions of 1,4-dioxene and benzophenone or p-benzoquinone under oxygen pressure affords the 1,2,4-trioxanes 4a,b ( cis ring junction by NOE 1H-NMR differential spectroscopy), resulting from trapping of the corresponding triplet preoxetane diradicals.

Dye laser tunable over the 217-3100-nm range

Tunable dye lasers have many applications in laser photochemistry, spectroscopy, and other areas. In this work some characteristics of a dye laser tunable in the 217-3100-nm range and pumped by a nitrogen laser ''Krona-1'' were studied. The 360-800-nm spectral range was covered with 20 organic compounds an their mixtures for the narrow-band dye laser. The maximum pulse power of the first and second harmonics vs. wavelength is presented. The results indicate that frequency doubling in KB5 crystals can extend the tunable range of dye lasers in the UV to 217 nm and achieve a conversion efficiency of n less than or equal to 4.6% in the 217-255-nm range.

Laser photochemistry of polymers

Absorption spectra of poly(N-vinyl-carbazole) and related polymers in the excited singlet, triplet, cationic, and anionic states were measured by nanosecond and picosecond laser photolysis methods and compared with those of model bichromophoric compounds. Absorption spectral shape of the excited singlet and cationic states is a function of polymer structure and sensitive to relative geometrical structure of two carbazolyl groups. The excited singlet species in poly(N-vinylcarbazole) are the sandwich excimer, the excited dimer with the partial overlap structure between two chromophores, and the so-called second excimer. The formation process of the sandwich excimer consists of an instantaneous rise and a slow one with a time-constant of a few hundred ps. The absorption spectrum of poly(N-vinylcarbazole) cation can be reproduced by a superposition of absorption bands of the sandwich dimer cation, the dimer cation with the partial overlap, and the dimer cation with the open form. On the other hand, absorption spectra of the triplet and anionic polymers are similar to those of the corresponding monomer model compound, showing a very weak interchromophoric interaction. All these results indicate that electronic excitation and charge in these polymers are not delocalized over several chromophores but trapped in some monomer and dimer sites. Dynamic behavior such as conformational change, intersystem crossing, photochemical formation yield of ion radicals, and their decay kinetics was also studied in detail.

Laser photochemistry with polarized light in low-temperature glasses

Laser photochemistry with polarized light in low-temperature glasses

Chiroptical studies of saturated ketones partially photoresolved by chiral laser photochemistry

Partial photoresolution of tricyclo[5.4.0.0 1,5]undecan-5-one ((±)- 1) with circularly-polarised 333.6 nm light from an Ar-ion c.w. laser led to Δε max= -0.40 and Δε/ε max = 1.8% at 300nm in n-hexane and 1S, 7R, 5R configuration for (-)- 1.

Infrared laser photochemistry of silane-hydrochloric acid mixtures

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInfrared laser photochemistry of silane-hydrochloric acid mixturesC. B. Moore, J. Biedrzycki, and F. W. LampeCite this: J. Am. Chem. Soc. 1984, 106, 25, 7761–7765Publication Date (Print):December 1, 1984Publication History Published online1 May 2002Published inissue 1 December 1984https://doi.org/10.1021/ja00337a019RIGHTS & PERMISSIONSArticle Views78Altmetric-Citations14LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (534 KB) Get e-Alerts Get e-Alerts

Raman evidence for the photochemical formation of cyanide from acetonitrile on copper electrodes

Laser Raman spectra from the system: Cu/CH 3CN, NaClO 4, H 2O, reveal evidence for cyanocopper(I) species in the interfacial region. The cyanide appears to originate in the laser-assisted decomposition of coordinated acetonitrile in O 2-rich aqueous electrolyte. The evidence for the involvement of laser photochemistry comes from uniform laser-flux perturbations of the cyclic voltammetry for the system. Parallel studies for the corresponding silver electrode system reveal evidence for the exhaustive, and probably laser-assisted, electro-oxidation of acetonitrile into nitrates and carbonates.