Flash photolysis of trimethylantimony and trimethylbismuth and the quenching of excited antimony and bismuth atoms

Abstract

The flash photolysis of Sb(CH3)3 and Bi(CH3)3 has been studied by kinetic absorption spectroscopy and emission spectroscopy. Several excited states of the metal atoms were detected, together with band systems of Sbz and Biz. Several unidentified band systems, one of which is tentatively assigned to BiCH,, were also observed. In the presence of O2 or CO, in the Bi(CH3)3 system the spectrum of BiO appeared, indicating excitedbismuth-sensitized decomposition. Quenching studies were carried out with several gases and relative quenching efficiencies determined. An interesting observation is reported o n the alteration of relative radiative transition probabilities from a given atomic level in induced emission as compared to spontaneous emission. he transfer of electronic excitation energy is of in-T herent interest in photochemistry and of practical importance in the study of photosensitization reactions. Molecular photosensitization has been investigated in considerable depth' both from a mechanistic and a synthetic viewpoint, but little is known concerning energy transfer from atomic species. Even the quenching of excited mercury,* the subject of the earliest and the most extensive study, is not yet well understood. Other atomic systems which have been investigated include cadmium, 3,4 alkali metal^,^ arsenic,6 oxygen,' thallium,8 and lead.s Spin-orbit relaxation of iodine, lo selenium," iron,I2 and arsenic6 has also been studied, but in these cases the amount of energy to be transferred is rather small (< 1 eV) and the factors governing relaxation are somewhat different.Recent experiments in this laboratory4 have shown that volatile alkylmetal compounds provide a useful flash-photolytic source of metal atoms. We have used this technique to produce excited antimony and bismuth atoms in an attempt to extend the limited amount of data available on electronic energy transfer from excited atomic species and to investigate some of the more important processes occurring in collisions of excited atoms with molecules. Experimental SectionA conventional flash-photolysis apparatus, with a 75-cm long quartz flash lamp and reactions cell, was employed. Spectra were recorded with Hilger medium or large quartz spectrographs on Kodak 103a-0 plates sensitized for the far-uv by sodium salicylate and developed for 3.5 min in Kodak D19 developer. Numerical (1) J. G. Calvert and J. N. Pitts, "Photochemistry," Wiley, New York, (2) R. J. CvetanoviC, Progr. React. Kinet., 2, 39 (1964); H. E. Gun-(3) S. Tsunashima, S. Satoh, and S. Sato, Bull. Chem. SOC. Jap., 42, (4) P. J. Young, G . Greig, and 0. P. Strausz, J. Amer. Chem. Soc.,

Suppression of electrical breakdown phenomena in liquid TriMethyl Bismuth based ionization detectors

“…In an electrical breakdown (in the gas phase), TMBi decomposes via an exothermic redox reaction into lower methyl bismuth species including (CH 3 )Bi and (CH 3 ) 2 Bi [47]. Similar decomposition products are generated during the electron bombardment in the ion source of a quadrupole mass spectrometer (PrismaPro QMG 250 M3, Pfeiffer Vacuum GmbH, Germany) (see figure 2).…”