Argon double

Thermal electrocyclizations of perhalogenated 1,3-butadienes yield perhalogenated cyclobutenes which can be solvolysed to 3,4-dihydroxy-3-cydobutene-l,2-dione ( squaric acid") and its derivatives (G. Maahs, 1966 H. Knorr, 1978 A.H. Schmidt, 1978). Double CO extrusion from fused cyclobutenediones has been used to produce cycloalkynes, e.g., benzyne from benzocyclobutenedione by irradiation in an argon matrix (O.L. Chapman, 1973) and cyc/o-Ci8, cyclo-Cn, etc. by laser desorption mass spectroscopy of appropriate precursors (see section 4.9.8). 

The U.S. military specification, M1L-P-27201B, requires 95% para content, 99.995% minimum hydrogen by difference, 50 vppm maximum total imputities, 9 vppm maximum combined nitrogen, water, and volatile hydrocarbons, 1 vppm maximum combined oxygen and argon, 39 vppm maximum helium, 1 vppm maximum carbon monoxide and dioxide, and a 10/40 micrometers nominal /absolute particulate filtration level. Liquid hydrogen is stored in double-walled vessels with evacuated pedite or multilayer insulation and transported in similarly insulated 50,000-L trailers or 900,000-L barges. 

Four IR absorption bands have been identified in the spectrum of the hydroxysulfonyl radical (HOSO 2) which has been obtained by the reaction of hydroxyl radicals with sulfur dioxide in argon matrix at 11 K16. The observed bands at 3539.9 and 759.5 cm 1 have been assigned to O—H and S—OH stretching modes while the bands at 1309.2 and 1097.3 cm-1 have been assigned to the asymmetric and symmetric stretching modes of the double bonded S02 moiety. These data are consistent with the theoretical prediction on the geometry of the hydroxysulfonyl radical12. 

Dye lasers, which can lase in either pulsed or CW formats. They may be pumped by flashlamps or by other lasers such as copper vapor, argon ion or by frequency doubled Nd YAG lasers. 

In-sltu Raman experiments were performed on a Spex 1401 double monochrometer Raman spectrometer, using a Spectra-Physlcs Model 165 argon Ion laser with an exciting wavelength of 5145 A. The In-sltu Raman cell consists of a quartz tube situated In a temperature controlled heating block. The Raman spectra were collected In the 180° backscatterlng mode. 

Fluorescence Lifetimes. Fluorescence lifetimes were determined by the phase shift method, utilizing a previously-described phase fluorimeter. The emission from an argon laser was frequency doubled to provide a 257 nm band for excitation. Fluorescence lifetimes of anisole and polymer 1 in dichloro-methane solution were 2.2 and 1.4 nsec, respectively. Fluorescence lifetimes of polymer films decreased monotonically with increasing DHB concentration from 1.8 (0) to 0.7 nsec (9.2 x 10 3 MDHB). Since fluorescence lifetimes (in contrast to fluorescence intensities) are unaffected by absorption effects of the stabilizer, these results provide direct evidence in support of the intensity measurements for RET from polymer to stabilizer. 

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