Narrow saturation resonances in the spectrum of OsO4 induced by CO2 laser radiation

Narrow saturation resonances in the v₃ band of the rotational-vibrational spectrum of the OsO₄ molecule were observed in the radiation field of a number of lines of the CO₂ laser. The parameters and relative positions of narrow resonances offer the possibility for further improvement of the long-term frequency stability of the CO₂ laser. The OsO₄ molecule is considered a suitable medium for finding the effect suggested by Letokhov; it consists in the γ-radiation narrow resonances on nuclear transitions of Os under the effect of excitation of OsO₄ molecular oscillations by the CO₂ laser radiation.     

Excitation and dissociation of polyatomic molecules under the action of femtosecond infrared laser pulses

The effect of high-intensity femtosecond laser pulses (100–200 fs) in the near (0.8–1.8 μm) and medium (4.6–5.8 μm) IR ranges on the CF₂HCl, CF₃H, (CF₃)₂C=C=O, and C₄F₉COI molecules is examined. Irradiation of CF₂HCl and CF₃H molecules by 0.8-to 1.8-μm laser pulses with intensities of >40 TW/cm² (>4 × 10¹³ W/cm²) makes them dissociate to yield CF₃H and CF₄, respectively. The key mechanism of the dissociation of these molecules is field ionization and fragmentation. The excitation of the stretching vibrations of the C=O bond in the (CF₃)₂C=C=O and C₄F₉COI molecules by 4.5-to 5.8-μm femtosecond pulses produced no detectable dissociation up to a fluence of ∼0.5 J/cm² (or a intensity of ∼2.5 TW/cm²). Probable explanations of this observation are discussed. Original Russian Text ? V.M. Apatin, V.O. Kompanets, V.B. Laptev, Yu.A. Matveets, E.A. Ryabov, S.V. Chekalin, V.S. Letokhov, 2007, published in Khimicheskaya Fizika, 2007, Vol. 26, No. 4, pp. 18–25.     

Femtosecond Infrared Laser Spectroscopy of Characteristic Molecular Vibrations in Bacteria in the 6-µm Spectral Range

JETP Letters - The transmission spectra of femtosecond laser pulses in the mid-IR range (5–6.6 μm) were investigated of submonolayer of Staphylococcus aureus and Pseudomonas aeruginosa...     

Rate constants and isotope effects for the reaction of H-atom abstraction from RH substrates by PINO radicals

The kinetics of the reactions of hydrogen atom abstraction from the C–H bonds of substrates of different structures by phthalimide-N-oxyl radicals is studied. The rate constants of this reaction are measured and the kinetic isotope effects are determined. It is shown that in addition to the thermodynamic factor, Coulomb forces and donor–acceptor interactions affect the reaction between phthalimide-N-oxyl radicals and substrate molecules, altering the shape of the transition state. This favors the tunneling of hydrogen atoms and leads to a substantial reduction in the activation energy of the process.     

Kinetics and mechanism of the addition of the phthalimid-n-oxyl radical to the double bond of vinyl compounds

The kinetics of the decomposition of the phthalimid-N-oxyl radical (PINO) in acetic acid has been studied. The rate constants of the addition of the radical to T bonds of molecules of vinyl compounds – styrene, methyl methacrylate, acrylonitrile, and methyl acrylate – have been measured. It was shown that electron-donor substituents in the monomer molecule increase, while electron-acceptor substituents decrease the rate of addition. The reactivity of monomers in the elementary step of addition of the PINO radical decreases in the order CH₂=C(CH₃)C₆H₅ > CH₂=CHC₆H₅ > CH₂=C(CH₃)COOCH₃ > CH₂=CHCOOCH₃ > CH₂=CHCN.     

Direct observation of the vibrational energy redistribution in (CF<Subscript>3</Subscript>)<Subscript>2</Subscript>CCO molecules resonantly excited by femtosecond infrared laser radiation

The dynamics of multiphoton excitation of (CF₃)₂CCO molecules has been investigated under the condition of resonant action of femtosecond infrared laser radiation on the ν₁ vibrational mode of the C=C=O bond. It has been shown that the mode-selective excitation of this vibration occurs up to the ν = 6 level. The kinetics of the subsequent intramolecular vibrational energy redistribution from the ν₁ mode has been measured. A value of 5 ± 0.3 ps has been obtained for the characteristic time of this process.     

<Emphasis Type="Italic">N</Emphasis>-hydroxyphthalimide-initiated radical polymerization of vinyl monomers

The initiating ability of N-hydroxyphthalimide in polymerization of methyl methacrylate and acrylonitrile was examined. For the polymerization of methyl methacrylate, the initial polymerization rates and activation energies were determined, and the dependences of the polymerization rates on the initiator and monomer concentrations were evaluated. An initiation mechanism was suggested.