Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results

The chromosphere is a thin layer of the solar atmosphere that bridges the relatively cool photosphere and the intensely heated transition region and corona. Compressible and incompressible waves propagating through the chromosphere can supply significant amounts of energy to the interface region and corona. In recent years an abundance of high-resolution observations from state-of-the-art facilities have provided new and exciting ways of disentangling the characteristics of oscillatory phenomena propagating through the dynamic chromosphere. Coupled with rapid advancements in magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly investigate the role waves play in supplying energy to sustain chromospheric and coronal heating. Here, we review the recent progress made in characterising, categorising and interpreting oscillations manifesting in the solar chromosphere, with an impetus placed on their intrinsic energetics.Comment: 48 pages, 25 figures, accepted into Space Science Review

Charge transfer kinetics in fullerene-oligomer-fullerene triads containing alkylpyrrole units

A photoinduced electron-transfer reaction has been observed in three fullerene-donor-fullerene triads containing an electron-rich pyrrole ring in the donor moiety. The kinetics of charge separation in solution has been investigated by photoluminescence and transient absorption spectroscopy. The polarity of solvent and the distance between donor and acceptor affect the forward electron-transfer reaction, in qualitative agreement with a semiempirical model for the Gibbs free energy for charge separation. Depending on the conditions, charge separation occurs at a rate of 10(9)-10(10) s(-1). The charge recombination rate is estimated to be faster than 2 x 10(10) s(-1). The relatively large contribution of the singlet-excited-state S-

Charge Transfer Kinetics in Fullerene-Oligomer-Fullerene Triads Containing Alkylpyrrole Units

A photoinduced electron-transfer reaction has been observed in three fullerene-donor-fullerene triads containing an electron-rich pyrrole ring in the donor moiety. The kinetics of charge separation in solution has been investigated by photoluminescence and transient absorption spectroscopy. The polarity of solvent and the distance between donor and acceptor affect the forward electron-transfer reaction, in qualitative agreement with a semiempirical model for the Gibbs free energy for charge separation. Depending on the conditions, charge separation occurs at a rate of 10e9-10e10 s-1. The charge recombination rate is estimated to be faster than 2 × 10e10 s-1. The relatively large contribution of the singlet-excited-state Sn ← S1 absorption of the fullerene moiety to the photoinduced absorption hampered a more accurate determination of the recombination rate.

Supramolecular Fullerene Architectures By Quadruple Hydrogen Bonding

The synthesis and full characterization of a quadruple bonded fullerene dimer using self-complementary 2-ureido-4[1H]-pyrimidinone units with high dimerization constants is described. The chemical integrity of the monomeric moiety in either compound is fully preserved, also with respect to its redox and UV-Vis behavior. Two novel supramolecular dyads consisting of an oligo(p-phenylene vinylene) (OPV) donor and fullerene (C60) acceptor are created via quadruple hydrogen bonding upon mixing the fullerene dimer and an OPV dimer. In these supramolecular dyads, singlet-energy transfer from the excited OPV unit to the fullerene causes a strong quenching of the OPV fluorescence. The high association constant of the 2-ureido-4[1H]-pyrimidinone quadruple hydrogen-bonding unit results in high quenching factors (Qmax ≥ 90). The lower limit obtained for the rate constant for energy transfer (kEN ≥ 6 × 10e10 s-1) is rationalized in terms of the Förster mechanism.

Supramolecular fullerene architectures by quadruple hydrogen bonding

The synthesis and full characterization of a quadruple bonded fullerene dimer using self-complementary 2-ureido-4[1H]-pyrimidinone units with high dimerization constants is described. The chemical integrity of the monomeric moiety in either compound is fully preserved, also with respect to its redox and UV-Vis behavior. Two novel supramolecular dyads consisting of an oligo(p-phenylene vinylene) (OPV) donor and fullerene (C60) acceptor are created via quadruple hydrogen bonding upon mixing the fullerene dimer and an OPV dimer. In these supramolecular dyads, singlet-energy transfer from the excited OPV unit to the fullerene causes a strong quenching of the OPV fluorescence. The high association constant of the 2-ureido-4[1H]-pyrimidinone quadruple hydrogen-bonding unit results in high quenching factors (Qmax ≥ 90). The lower limit obtained for the rate constant for energy transfer (kEN ≥ 6 × 10e10 s-1) is rationalized in terms of the Förster mechanism.

Preferential Hetero-dimer Formation And Equilibrium Dynamics Of Self-complementary Bifunctional Oligo(p-phenylenevinylene) And C60 Ureido-pyrimidinone Derivatives In Solution

The formation of hetero-dimers of bifunctional oligo(p-phenylenevinylene) and C60 ureido-pyrimidinone derivatives has been observed by 1H-NMR and fluorescence techniques.