A difference detection system for high precision measurements of ultrafast transmission changes

Ultrafast transmission changes can be recorded with high precision by means of a difference detection system. Using single pulses of low energy (0.1 nJ) and low repetition rate, variations of the transmitted energy induced by an excitation pulse are measured with an accuracy of 10-4

Generation of frequency shifted picosecond pulses with low temporal jitter

Transient stimulated Raman scattering is used for the generation of a frequency shifted picosecond light pulse; part of this Raman shifted pulse is subsequently coherently scattered at a material excitation of a second Raman cell. Starting with the second harmonic pulse (tp = 4 ps) of a mode-locked Nd : glass laser system, both the stimulated and the coherently produced pulses have durations of 2.3 ps at different wavelengths. By the appropriate choice of the Raman medium pulses between 13 000 and 21 000 cm-1 can be generated. The coherent generation process minimizes the temporal jitter between the two pulses and allows to obtain a high time resolution of better than 0.3 ps in excite and probe experiments

New Results on Ultrafast Coherent Excitation of Molecular Vibrations in Liquids

Coherent Raman probe scattering experiments are performed to study dynamical processes of polyatomic liquids at 300 K. For single homogeneous transitions the dephasing timeT 2 is readily obtained from time resolved investigations. Spectral studies show an interesting time dependent shift in scattered frequency. After the excitaiton the vibrating molecules are shown to relax freely with their resonance frequency. Multiple, equally spaced transitions exhibit a beating phenomenon which provides the dephasing time and the frequency interval between neighboring vibrational states. Inhomogeneously broadened systems do not allow a ready determination of the dephasing time by the present probing technique. Previous experiments on the subject have to be reconsidered

The British Crown in the Spotlight of Literary and Cultural Studies: Analyzing Past and Present ‘Myths of the Monarchy’

Die insgesamt elf Artikel des von Anette Pankratz und Claus-Ulrich Viol herausgegebenen Sammelbands (Un)making the Monarchy analysieren ein breites Spektrum an kulturellen Phänomenen, die auf vielfältige Weisen mit der britischen Monarchie in Zusammenhang stehen. Die Fallstudien beschäftigen sich unter anderem mit Mode, Literatur, Satire und monarchiekritischen politischen Tendenzen. Durch seine dezidiert literatur- und kulturwissenschaftlichen Herangehensweisen eröffnet der Band neue Sichtweisen auf zentrale Anliegen der Monarchieforschung, allen voran die Frage nach den Gründen für die anhaltende Attraktivität der britischen Monarchie. Trotz des konstruktivistischen Ansatzes der Artikel beleuchten die einzelnen Texte konkrete soziokulturelle, soziopolitische und sogar psychologische Auswirkungen der „myths of monarchy“ (S. 17) auf die britische Gegenwartsgesellschaft.Anette Pankratz and Claus-Ulrich Viol’s edited volume (Un)making the Monarchy comprises eleven articles that aim at analyzing (contemporary) phenomena surrounding the British monarchy in cultural fields as varied as fashion, literature, satire, or anti-monarchist political tendencies. With its prevailing cultural and literary studies perspectives, the volume addresses in an innovative way timely and pressing questions in the field of royal studies, among them the question for the reason of the unrelenting appeal of this ancient institution. Despite an overall constructivist stance, the articles in the volume draw on very concrete socio-cultural, socio-political, and even psychological effects that the “myths of monarchy” (p. 17) have on contemporary British society

Energy transfer from retinal to amino acids — a time-resolved study of the ultraviolet emission of bacteriorhodopsin

Two-step excitation of retinal in bacteriorhodopsin by visible light is followed by an energy transfer to amino acids that is seen as fluorescent emission around 350 nm. The fluorescence spectrum obtained after two-step excitation (2 × 527 nm) differs from the fluorescence spectrum obtained after one-step ultraviolet excitation (263.5 nm) by a strongly quenched emission with a fluorescence lifetime of 10 ± 5 ps and a smaller spectral width. The two-step absorption process presumably selects tryptophan residues which strongly couple to the retinal chromophore

Early picosecond events in the photo cycle of Bacteriorhodopsin

The primary processes of the photochemical cycle of light-adapted bacteriorhodopsin (BR) were studied by various experimental techniques with a time resolution of 5 × 10-13 s. The following results were obtained. (a) After optical excitation the first excited singlet state S1 of bacteriorhodopsin is observed via its fluorescence and absorption properties. The population of the excited singlet state decays with a lifetime τ1 of ~0.7 ps (430 ± 50 fs) (52). (b) With the same time constant the first ground-state intermediate J builds up. Its absorption spectrum is red-shifted relative to the spectrum of BR by ~30 nm. (c) The second photoproduct K, which appears with a time constant of τ2 = 5 ps shows a red-shift of 20 nm, relative to the peak of BR. Its absorption remains constant for the observation time of 300 ps. (d) Upon suspending bacteriorhodopsin in D2O and deuterating the retinal Schiff base at its nitrogen (lysine 216), the same photoproducts J and K are observed. The relaxation time constants τ1 and τ2 remain unchanged upon deuteration within the experimental accuracy of 20%

Excited-state reaction dynamics of bacteriorhodopsin studied by femtosecond spectroscopy

The photodynamics of bacteriorhodopsin were studied by transient absorption and gain measurements after excitation with femtosecond pulses at 620 nm. With probing pulses at longer wavelengths (λ > 770 nm) the previously reported formation of the J intermediate (with a time constant of 500±100 fs) was confirmed. With probing pulses around 700 nm, a faster process with a relaxation time of 200±70 fs was observed. The data analysis strongly suggests that this kinetic constant describes the reactive motion of the polyatomic molecule on its excited-state potential energy surface, i.e. one observes directly the incipient isomerization of the retinal molecule. The minimum of the S1 potential energy surface reached in 200 fs lies approximately 13300 cm−1 above the ground state of bacteriorhodopsin and from this minimum the intermediate J is formed with a time constant of 500 fs