Occurrence of highly endoergic chemiluminescent reactions was observed using laser ablation of metal targets for Al + NH3, Al + H2O and Mg + O2 systems. Observed chemiluminescent species were AlH (A1Π), AlN (A3Πi), AlO (B2Σ+) and MgO (B1Σ+).
A method is described for designing FIR lowpass filters for receivers and transmitters in data transmission systems. Choosing both filters as a matched pair, the objective is to provide each filter with quasi‐equiripple stopband attenuation and to make the overall impulse response satisfy zero intersymbol interference (zero ISI). The method consists of four steps. First, the ideal overall transfer characteristics are approximated in terms of a Fourier series, and the initial zeros of the characteristics are obtained. Second, one half of the mirror image zeros are used for finding zeros on a unit circle so that the single filter has equiripple stopband characteristics. Third, in the overall transfer function, these stopband zeros are fixed as double zeros. The overall impulse response is successively approximated by changing the mirror image zeros in the passband so that the zero ISI condition is satisfied. Finally, the obtained mirror image zeros are divided into two groups, one is allotted to the transmission filter and the other is to receiving filter so that they form a matched pair. In the zero ISI approximation in the third stage, a good initial response is obtained. Further, since the number of variables is equal to the number of zero ISI conditions, the approximation converges accurately and quickly. As a design example, a filter pair is shown in which both the transmission and receiving filters are 59th orders. The ISI is only 2.2 × 10‐4% compared to 0.4% found in a different design method.
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