No abstract

presence of C=0 and SiMe but no Si-O-Si groups. UV maxima was found at 305 nm.The present new method of preparing polysilylenes is quite versatile in designing new polymers. The work is supported in part by the Ministry of Education, Science, and Culture (Grant-in-Aid for Special Project Research, No. 63106003).

We demonstrate the in situ identi cation of crack cocaine and cocaine•HC l by using a ber-optic Raman probe and a portable Raman spectrograph. The Raman spectru m of freebase cocaine (crack) is obtained in just seconds without any sample preparation, and differs signi cantly from that of cocaine•HCl. We also show that the Raman spectra of these drugs are easily distinguishable from comm on cutting agents and impurities such as benzocaine and lidocaine. Another advantage of using Raman spectroscop y is that the drugs can be identi ed while contained in transparent containers, such as clear plastic evidence containers that are used to store drug evidence and to maintain chain of custody. W e also demonstrate the in situ Raman identi cation of drugs separated by thinlayer chrom atography. We discuss the utility of surface-enhanced Raman spectroscopy (SERS) in toxicological drug screen ing and present prelim inary SERS data for cocaine in solution using colloidal silver. We believe this to be the rst published SERS spectru m of freebase cocaine.

No abstract

The dynamics of the dec^y of the tautomer species and triplet state of 3-hydroxyflavone have been studied in detail by transient absorption, two-step las4r excitation, and steady-state photolysis experiments. The decay of the tautomer species is observed to be 6.9 X 104 s'1 in «¡heptane at room temperature and is only slightly dependent on various chosen nonpolar solvents. This rate is more than p orders of magnitude smaller than the rate of excited-state proton transfer, in agreement with the experimental results reported by Itoh et al. The bimolecular quenching rate constant of the tautomer of 3-hydroxyflavone by oxygen is determine^t o be 3.2 x 109 M"1 s"1 in «-heptane. Two proposed mechanisms that involve the tautomer ground state and triplet state for the reverse proton transfer are presented in order to interpret the experimental results. An observed T[ -T" absorption in the transient absorption spectrum at -395 nm is assigned as originating from the normal species with a 7.2-µ8 lifetime in «-heptane. The yield of the triplet states is determined to be 0.18 ± 0.02 as a lower limit.