ISSN:0951-4198    

DOI:10.1002/rcm.1290030202

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

ISSN:0951-4198    

DOI:10.1002/rcm.1290030203

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractThe energetics of S 2+·ion formation in electron dissociative ionization of linear CS2are investigated experimentally with a crossed‐beam apparatus.Ab initioself‐consistent‐field molecular orbital (SCF MO) calculations of potential energy curves for low‐lying electronic states of this ion have been made in order to explain how stable S 2+·ions are formed, initially at the very large internuclear separa

ISSN:0951-4198    

DOI:10.1002/rcm.1290030204

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractThe electron ionization and chemical ionization mass spectrometry of some diastereomeric β‐hydroxy‐γ‐fluoro alkyl aryl sulphoxides is described and the mechanisms of the common fragmentation patterns are discussed with the aid of linked scans at constant B/E and at constant B2/E, mass‐analysed ion kinetic energy spectra and labelling ex

ISSN:0951-4198    

DOI:10.1002/rcm.1290030205

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractCollision‐induced dissociation of peptide ions yields „sequence”︁ ions arising from dissociations of the peptide backbone. Recently, Biemann and his collaborators have elucidated fragment ions involving cleavage of all or part of the side‐chains, and have characterized them as remote‐site fragmentations of the type investigated for other molecular species by Grosset al. The present work reports results of experiments conducted using a tandem, hybrid mass spectrometer, and devoted to investigating whether remote‐site fragmentations (including side‐chain cleavages for peptide ions) can be observed for collision energies substantially lower than the keV range used previously. It was found that (laboratory‐frame) collision energies of at least 200 eV, and preferably greater, are required for the formation of such fragments. At collision energies in this range the transmission efficiency of the qQ assembly is much lower than for the more usual range of a few tens of eV; this drop in transmission efficiency becomes increasingly severe with increasing mass

ISSN:0951-4198    

DOI:10.1002/rcm.1290030206

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractRoom temperature ion/molecule reactions in 0.30 Torr of helium, carried out in a flowing afterglow, show that the gas‐phase acidity of nitrobenzene is intermediate between those of ethanol and isopropanol, in contrast to published high‐pressure mass spectrometer data. The revised gas‐phase acidity of nitrobenzene, ΔHºacid(C6H5NO2) = 377 ± 3 kcal mol−1, is shown to be consistent with known acidifying effects when a hydrogen atom is replaced by a nitro group in a Brönsted acid. Additional reactions involving nitrobenzene or its conjugate bas

ISSN:0951-4198    

DOI:10.1002/rcm.1290030207

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractThe negative ion mass spectra or trimethylsilylzeatin riboside and t‐butyldimethylsilylzeatin, generated using either ammonia or 10% CO2/Ar as reagent gas, are described. Optimal yields of [M‐H]−ions were obtained with a source pressure of 5 Pa in the electron ionization source of a ZAB‐2F mass spectrometer, compared with 15 Pa to generate [M+H]+in the chemical ionization mode. At 15 Pa no negative ions could be o

ISSN:0951-4198    

DOI:10.1002/rcm.1290030208

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

ISSN:0951-4198    

DOI:10.1002/rcm.1290030209

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

ISSN:0951-4198    

DOI:10.1002/rcm.1290030210

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

ISSN:0951-4198    

DOI:10.1002/rcm.1290030211

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY