摘要:

Triplet-state benzophenone rapidly sensitized the photoreduction of Cu(acac)2in alcohols to give polymeric Cu(acac) as black precipitates. The binary complexes of Cu(acac) of polypyridines, polysulfide, olefins, acetylenes, and carbon monoxide could be generated in solution under an inert atmosphere when a ligand was presentinsituduring photoreduction or added after an appropriate photoreduction was completed. Except Cu(acac)—(PPh3)2, the Cu(acac) complexes of various ligands are sensitive to air oxidation, but show a wide range of reactivity towards disproportionation and photolysis. In the presence of terminal acetylenes, amorphous copper(I) acetylides were isolated in good yields.

ISSN:0008-4042    

DOI:10.1139/v83-146

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Bis(acetylacetonato)copper(II), Cu(acac)2, quenches triplet excited states of ketones and polynuclear aromatic hydrocarbons efficiently, but only aromatic ketones with high triplet energy successfully sensitize photoreduction of Cu(acac)2in alcohols under nitrogen to give derivatives of aeetylacetonatocopper(I), Cu(acac). For the triplet state benzophenone-sensitized photoreduction of Cu(acac)2, the quantum yields of photoreduction (ΦC) and those of benzophenone disappearance (ΦB) were determined in methanol with various concentrations of Cu(acac)2. The values of the quenching rate constant,kq, determined from these two types of monitors on the basis of the proposed mechanism were in good agreement (6.89 ~ 7.35 × 109 M−1 s−1). This value was higher, by a factor of about two, than that obtained from the monitor of the benzophenone triplet decay rates generated by flash photolysis in the presence of Cu(acac)2. The quenching rate constants of various aromatic ketone and hydrocarbon triplet states by Cu(acac)2were determined by flash photolysis to be in the order of the diffusion rate constant and the quantum yields of these photoreductions were found to be far from unity. Paramagnetic quenching, with contributions of electron exchange and charge transfer, was proposed as a possible quenching mechanism. For a series of aromatic ketone sensitizers with higher triplet energy, this mechanism was used to rationalize the observed high quenching rate constants in contrast to the low quantum yields of photoreduction.

ISSN:0008-4042    

DOI:10.1139/v83-147

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The infrared and resonance Raman spectra of the two long-lived forms of triphenylformazan and several of its derivatives have been examined. The spectra of unsymmetrically15N-labelled derivatives suggest that two tautomers exist for each of the two forms. This observation is confirmed by the spectra of 1-(p-halophenyl)-3,5-diphenylformazans. The spectra of the non-chelate forms of these latter compounds demonstrate that the position of the tautomeric equilibrium is influenced by the electron-attracting ability of thepara-halo-substituent. A comparison of the resonance Raman spectra of the two forms leads to the conclusion that excited state proton transfer is the initial photoevent in the photochromism of the triphenylformazans.

ISSN:0008-4042    

DOI:10.1139/v83-148

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The increasing density of devices in large scale integrated circuits has created a need for lithographic techniques that have higher resolution (≈1 μm) than can be achieved with conventional (≈400 nm) optical technology. By operating in the deep uv (200–300 nm) region of the spectrum, one can reduce diffraction effects and increase resolution. Because of the high optical density of conventional photoresists in this wavelength range, new materials are needed. This paper presents an overview of new positive resists that we have developed. These include methacrylate polymers that undergo photochemical chain scission and two-component (photosensitive solution inhibitor – alkali soluble matrix resin) syst

ISSN:0008-4042    

DOI:10.1139/v83-149

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

In order to characterize unambiguously photochemical energy absorption and subsequent intramolecular relaxation dissociation, collision-free conditions are required. Isolated molecule photochemistry may be studied in a quadrupole ion store (QUISTOR) under near collision-free conditions. Photodissociation of primary ions, H2+and CH4+, has been described and we have reported on the slow multiphoton induced dissociation of protonated dimers of 2-propanol in the infrared region. Ions may be trapped in a QUISTOR in either a total storage mode wherein ions of different masses are stored simultaneously, or a mass selective mode wherein single ion species are isolated. Utilization of the QUISTOR as an ion/molecule reactor in the total ion storage mode facilitates the formation of secondary ions chosen for study, their isolation, and irradiation. Determination of the ranges of ion masses which may be stored in each mode is described. In the total storage mode, ion mass-to-charge ratios tom/e 455 have been observed. Selective storage tom/e 219 is reported, though with poor resolution. The effects of variation in trapping parameters including drive frequency and physical dimensions of the device are discussed.

ISSN:0008-4042    

DOI:10.1139/v83-150

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

A versatile technique employing pulsed quadrupole ion storage mass spectrometry and a low power CW CO2laser for the study of slow infrared multiphoton dissociation of gaseous ions under collision-free conditions is described. Multiphoton dissociation of gaseous ions derived from isopropanol. 2-d1-isopropanol, isopropan-d-ol and perdeutcroisopropanol, with irradiation for up to 110 ms with intensities of ~20 W cm−2, was effected. Irradiation of proton (or D+) bound alcohol dimers showed that three dissociative reaction channels are utilized in multiphoton dissociation: the photodissociation yield for the dissociative reaction channel of lowest activation energy increases and becomes dominant with collisional and radiative relaxation of the ions. Of the three ionic photoproducts of multiphoton dissociation of proton bound alcohol dimers, only the protonated ether is found to be photodissociative under the prevailing conditions. The photochemical stability of the ion formed by loss of the elements of propene from the proton bound alcohol dimer contrasts sharply with the multiphoton dissociation of the proton bound alcohol–water mixed dimer, and serves to demonstrate the applicability of multiphoton dissociation to distinguish between gaseous ion isomers.

ISSN:0008-4042    

DOI:10.1139/v83-151

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

A previously-unknown ion-pair state of ICl has been identified and characterized in sequential transitions using polarization-labelling spectroscopy. This state is designated 1(3P1), indicating a state of axial electronic angular momentum Ω = 1 correlating diabatically at dissociation with the states I+(3P1) + Cl−(1S0) of the separated ions. The electronic energy and local potential constants for levels with ν = 1–7 are (in cm−1)Tc = 45552.805(23), ωc = 184.854(13), ωcxc = 0.6737(13),Bc = 0.058898(42), and α = 2.485(93) × 10−4, and the equilibrium bond distance is 3.231 Å.

ISSN:0008-4042    

DOI:10.1139/v83-152

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Photochemical and fluorescence studies of acetylene initiated by absorption of light in the vacuum ultraviolet have been described. The photochemical primary process consists of (1) the formation of C2 + H2, (2) the production of C2H + H, and (3) the formation of a metastable acetylene. The quantum yield of process (1) is about 0.1 and that of process (2) is 0.06 at 1849 Å and 0.3 at 1470 Å. The metastable acetylene either reacts with ground state acetylene to produce diacetylene or is deactivated by collisions with the walls, inert gases, or by fluorescence. A quasicontinuous emission is observed in the 4000 to 6000 Å region when acetylene is exposed to incident wavelengths below 1305 Å. This emission is ascribed to an electronically excited ethynyl radical. The rates of reaction C2H + H2 → C2H2 + H and C2H + RH → C2H2 + R (RH = CH4, C2H6, C3H8) have been measured. The photochemistry of acetylene in the Jovian and Titan atmospheres is briefly discussed.

ISSN:0008-4042    

DOI:10.1139/v83-153

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The photoisomerizations of protonated 5-methylhex-3-en-2-one and 4-methylpent-2-enoic acid have been examined. In each case a relatively rapidcis/transisomerization about the carbon–carbon partial double bond and a slower conversion to protonated dihydrofuran2Hor protonated lactone5H, respectively, were observed. The transformation of the acyclic cations to the five-membered ring cations was shown to occur by a photo-initiated, intramolecular hydride shift from the γ to β carbon atom. This shift is fully in accord with an excited state twisting/charge localization model for the excited states of these systems. Control experiments and the thermal chemistry of these ions is described.

ISSN:0008-4042    

DOI:10.1139/v83-154

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

A kinetic study of the reactions of OH radicals with a series of fluoroethanes in the gas phase is presented. OH radicals were generated by flash photolysis of H2O vapor in the vacuum uv (λ > 165 nm) and were monitored in absorption by time-resolved attenuation of resonance radiation at 308.15 nm [OH(A2Σ+ → X2Π)]. The following absolute rate constants (in units of 109 cm3mol−1 s−1at the 95% confidence limit) were determined atFrom a linear correlation of the present and previously published rate constants with bond dissociation energies, the following quantities (in kcal mol−1at 298 K) were estimated to be:D(CH3CHF—H) = 96.3 ± 1.5,D(CH2FCHF—H = 98.8 ± 1.0,D(CF3CHF—H) = 103.5 ± 1.0,D(CHF2CF2—H) = 103.0 ± 1.5, and

ISSN:0008-4042    

DOI:10.1139/v83-155

出版商:NRC Research Press    

年代:1983

数据来源: NRC