Chemiluminescence from Ni(CO)4 and Fe(CO)5 collisions with metastable He, Ne, and Ar atoms is described. The emission spectra are due to atomic Ni and Fe. An analysis of these spectra indicate a dissociative energy transfer process which is not spin–differentiated among the metal atom states. Because of this, certain low-lying quintet states are seen here in emission for the first time. Steady state population analysis of all features permits a determination of the radiative lifetimes of these new states. For both carbonyls, a restricted statistical rate theory, in which the CO fragments are allowed to translate in one dimension only (the radial reaction coordinate) and are prohibited from rotating, gives good agreement with all the data. The nature of metastable electronic energy transfer is compared to photolytic energization, and a comparison of the likely excited electronic states involved in each indicates the source of the differences in product distributions observed by each method.

Articles you may be interested inInteraction of wide band gap single crystals with 248 nm excimer laser radiation. V. The role of photoelectronic processes in the formation of a fluorescent plume from MgOThe reaction of hot hydrogen atoms with N 2 0 to form OH and N2 has been studied. The hot hydrogen atoms were generated by the photolysis of HI at 248 nm which produces a bimodal distribution of hydrogen atoms having 43.6 and 22.0 kcallmol of translat!on~l energy. The OH produced was monitored by laser-induced fluorescence in the A-X transition [(0,0) band]. The nascent rotational distribution of this hot reaction was found to be characterized by a Boltzman temperature of 4700 ± 300 K.

Time-resolved luminescence lifetime measurements are an important photophysical technique. However, access to this technique at the undergraduate level is limited by the expense of the instrumentation needed to create the well-defined light pulses required to measure the luminescence decay of an excited state molecule. We present here an inexpensive, improved light emitting diode (LED) circuit that is capable of supplying bright light pulses. Our circuit is designed to overdrive the LED resulting in a bright excitation light source with a well-defined square wave pulse shape. This allows for the facile measurement of luminescent molecules with decay lifetimes in the hundreds of nanoseconds to microsecond range. Data are presented for five UV, violet, and blue LEDs as driven by the improved circuit that can be used as a guide for selecting the best excitation light source for a particular molecule of interest. Our students have studied the quenching of aqueous tris­(bipyridine)­ruthenium­(II) chloride with ferric ion using an overdriven blue LED as an excitation source. While ferric ion is not an efficient quencher compared to molecular oxygen, it is much easier to handle, allowing for the preparation of accurate standard solutions free of dissolved oxygen.

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