Revival structure

F. Rosca-Pruna and M. J. J. Vrakking. Revival structures in picosecond laser-induced alignment of molecules. I. Experimental results. J. Chem. Phys., 116(15) 6567-6578 (2002). 

T. Seideman. Revival structure of ahgned rotational wave packets. Phys. Rev. Lett, 83(24) 4971 974 (1999). 

Fig. 2. Time dependence of a hydrogen wave-packet with averaged principal quantum number h = 80 and FWHM An = 4. On top we show the autocorrelation junction l(tp(t)l ip(0)[) and on bottom the radial expectation value. Both values document the occurrence of periodic structures as well as revival and partial revival structures as indicated by vertical dotted lines.

Here, long-time dynamics of an initially extremely cold ensemble of NaK molecules excited to its electronic A state are presented. This will allow a detailed observation of revival structures. As a rough estimate, the occurrence of the total revival can be calculated from spectroscopic data [357] to be at Trev 190 ps- The low temperature of the molecular beam, combined with its high stability and the extremely low pulse-to-pulse fluctuations of the laser system used, enabled for the first time the real-time detection of fractional revival structures in a molecular system. 

In the spectrogram for Na K (Fig. 3.34 a) the revival structure already recognizable in Fig. 3.31 a can be observed in detail. The initial oscillation with = 75.8cm loses intensity with increasing delay time. The... 

Similar results were obtained for two isotopes of the heteronuclear NaK molecule excited to its electronic A state. By means of spectrogram technique, the pronounced revival structure of the induced wave packet propagation was nicely illustrated. Higher order fractional revivals could be observed for the first time for a molecular system. Strong half and quarter revivals were observed at = 75 ps and = 40 ps for the lighter isotope... 

Gaff, D.F., Zee, S.T. O Brien, T.P. (1976). The fine structure of dehydrated and reviving leaves of Borya nitida Labill. - a desiccation tolerant plant. Australian Journal of Botany, 24, 225-36. 

In 1985, it was reported by Hsiang et al. [43] that the cytotoxic activity of 20-(S)-camptothecin (CPT III) was attributed to a novel mechanism of action involving the nuclear enzyme topo I, and this discovery of unique mechanism of action revived the interest in CPT and its analogues as anticancer agents. CPT stabilizes the covalent, reversible topo I-DNA complex leading to the inhibition of DNA synthesis in mammalian cells and interferes with the topo I breakage-reunion reaction [44]. Clinical trials and structure-activity relationships have demonstrated the requirement of the a-hydroxy group, the... 

There have also been revivals of the steam car. Robert McCulloch, the chain-saw millionaire, spent part of his fortune on a steam prototype, called the Paxton Phoenix, between 1951 and 1954. William Lear of Learjet fame, spent 15 million in 1969 on a turbine bus and a 250-horsepower turbine steam car. Both used quiet, efficient steam engines although the bus had reliability problems and poor gas mileage. Lear also tried to enter a steam car into the 1969 Indianapolis 500. The British firm of Austin-Healey was also working on a steam car in 1969. It had four-wheel drive. However, even prosperous entrepreneurs like McCulloch and Lear found that they lacked the means and support structure to successfully mass market a competitive car. Alternative power systems would have to wait until air-quality regulations resulted in some breakthroughs with hybrid and even fuel-cell cars. 

In the [Zn(2)2]2+ species, a single Zn2+ ion is able to revive the luminescence of all the 32 naphthyl units present in the two dendritic structures. This result shows that dendrimers can be profitably used as supramolecular fluorescent sensors for metal ions, as shown in Fig. 2. In this case, the sensor fluorescence is switched on upon metal ion coordination, and low Zn2+ concentrations (ca. 1 pM) can be easily detected. 

A first generation poly(amido amine) dendrimer has been functionalized with three calyx[4]arenes, each carrying a pyrene fluorophore (4) [30]. In acetonitrile solution the emission spectrum shows both the monomer and the excimer emission band, typical of the pyrene chromophore. Upon addition of Al3+ as perchlorate salt, a decrease in the excimer emission and a consequent revival of the monomer emission is observed. This can be interpreted as a change in the dendrimer structure and flexibility upon metal ion complexation that inhibits close proximity of pyrenyl units, thus decreasing the excimer formation probability. 1H NMR studies of dendrimer 4 revealed marked differences upon Al3+ addition only in the chemical shifts of the CH2 protons linked to the central amine group, demonstrating that the metal ion is coordinated by the dendrimer core. MALDI-TOF experiments gave evidence of a 1 1 complex. Similar results have been obtained for In3+, while other cations such as Ag+, Cd2+, and Zn2+ do not affect the luminescence properties of... 

The discussion and classification of reagents is masterful in identifying Ingold s new nomenclature and principles with more widely known oxidation-reduction and acid-base theory. The 1953 lectures at Cornell University, published as Structure and Mechanism in Organic Chemistry, follow this same strategy, showing how old classification schemes overlap with each other and how apparent inconsistencies disappear as old schemes are incorporated into the new one. Nineteenth-century Berzelian electrochemical dualism, revived by Lapworth and Robinson in the cationic/anionic schema, disappears into the electrophilic/nucleophilic language. 

These results, as well as rate studies " and kinetic isotope effects ", support a concerted, 5ptra-structured oxenoid-type transition state for the CH oxidations". The original oxygen-rebound mechanism has been discounted (see the computational work in Section I.D). Recently, however, the stepwise radical mechanism was revived in terms of the so-called molecule-induced homolysis , but such radical-type reactivity was severely criticized on the basis of experimental" and theoretical grounds. 

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