Bestimmung einzelner Pflanzenbestandteile

Ohne Zusammenfassung     

Rate coefficients for the reactions of O(3P) with selected biogenic Hydrocarbons

The rate coefficients for the reaction of O(³P) with the biogenic hydrocarbons Δ³-carene, α-pinene, and isoprene have been measured using a direct method for the first time. O(³P) was generated from the pulsed photolysis of NO₂ or O₃ at 308 nm, and measured by resonance fluorescence at 131 nm. Rate coefficients at room temperature for the biogenics are similar: (3.4 ± 0.6) × 10^?11, (3.7 ± 0.6) × 10^?11, and (3.5 ± 0.6) × 10^?11 cm³ molec^?1 s^?1, for Δ³-carene, α-pinene, and isoprene, respectively. The rate coefficients for the reaction of O(³P) with NO₂ and ethene were also measured with the same method, and these values are within 4% and 10% of the currently recommended values, respectively. The correlation between OH and O(³P)-alkene reaction rate coefficients is updated and discussed. © 1995 John Wiley & Sons, Inc.     

A study of the intersystem crossing reaction induced in gaseous sulfur dioxide molecules by collisions with nitrogen and cyclohexane at 27°C

The quantum yields of the sulfur dioxide triplet (³SO₂)-sensitized phosphorescence of biacetyl (Φ_sens) were determined in experiments with N₂–SO₂–Ac₂ and c-C₆H₁₂–SO₂–Ac₂ mixtures excited at 2875 Å at 27°C. The fraction of the biacetyl triplets which reacts homogeneously by radiative or nonradiative decay reactions was determined in a series of runs at constant [SO₂]/[M] and [SO₂]/[Ac₂] ratios but at varied total pressure. A kinetic treatment of the Φ_sens results and singlet sulfur dioxide (¹SO₂) quenching rate constant data gave the following new kinetic estimates: ¹SO₂ + M → (SO₂–M) (1b) ¹SO₂ + M → ³SO₂ + M (2b); for ¹SO₂–N₂ collisions, k_2b/(k_1b + k_2b) = 0.033 ± 0.008; for ¹SO₂–c-C₆H₁₂ collisions, k_2b/(k_1b ± k_2b) = 0.073 ± 0.024; previous studies have shown this ratio to be 0.095 ± 0.005 for ¹SO₂–SO₂ collisions. It was concluded that the inter-system crossing ratio in ¹SO₂ induced by collision is relatively insensitive to the nature of the collision partner M. However, the individual rate constants for the collision-induced spin inversion of ¹SO₂ (k_2b) and the total ¹SO₂-quenching constants (k_1b + k_2b) are quite sensitive to the nature of M: k_2b/k_2a varies from 0.10 ± 0.03 for M = N₂ to 1.11 ± 0.37 for M = c-C₆H₁₂, and (k_1b + k_2b)/(k_1a + k_2a) varies from 0.29 for M = N₂ to 1.44 for M = c-C₆H₁₂; k_1a and k_1b are the rate constants for the reactions ¹SO₂ - SO₂ → (2SO₂) (1a) and ¹SO₂ + SO₂ → ³SO₂ + SO₂ (2a), respectively.     

Time-resolved studies of ultrafast wavepacket dynamics in hydrogen molecules

Recent advances in the study of quantum vibrations and rotations in the fundamental hydrogen molecules are reported. Using the deuterium molecules (D₂⁺ and D₂) as exemplars, the application of ultrafast femtosecond pump-probe experiments to study the creation and time-resolved imaging of coherent nuclear wavepackets is discussed. The ability to study the motion of these fundamental molecules in the time-domain is a notable milestone, made possible through the advent of ultrashort intense laser pulses with durations on sub-vibrational (and sub-rotational) timescales. Quantum wavepacket revivals are characterised for both vibrational and rotational degrees of freedom and quantum models are used to provide a detailed discussion of the underlying ultrafast physical dynamics for the specialist and non-specialist alike.     

Dirac cohomology of the Dunkl-Opdam subalgebra via inherited Drinfeld properties

Abstract

In this paper, we define a new presentation for the Dunkl-Opdam subalgebra of the rational Cherednik algebra. This presentation uncovers the Dunkl-Opdam subalgebra as a Drinfeld algebra. We use this fact to define Dirac cohomology for the DO subalgebra. We also formalize generalized graded Hecke algebras and extend a Langlands classification to generalized graded Hecke algebras.     

13C NMR spectra of polymethoxy- and methylenedioxyflavonols

The ¹³C NMR spectra of 20 polymethoxy- and/or methylenedioxyflavonols are reported. In key cases assignments have been made by examination of fully coupled spectra.