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Microwave afterglow studies of electron-ion recombination at low temperatures

Thesis/Dissertation ·
OSTI ID:5013740
A specially constructed low temperature microwave afterglow mass spectrometer apparatus employing microwave heating of the electrons has been used to study the dissociative recombination of the complex molecular ions Ne/sub 3//sup +/, H/sub 3//sup +/, and H/sub 5//sup +/ with electrons. The measured electron decays in recombination controlled afterglows are fitted by computer solutions of the continuity equation containing recombination and ambipolar diffusion loss terms. At approx. = 80K and approx. = 6 Torr of neon, Ne/sub 3//sup +/ is the dominant afterglow ion. The recombination coefficient, ..cap alpha..(Ne/sub 3//sup +/), has been determined over the range 80K less than or equal to T/sub e/ less than or equal to 4000K, and the result may be expressed as ..cap alpha..(Ne/sub 3//sup +/) = (1.1 +/- 0.1) x 10/sup -6/((T/sub e/)/(300))/sup -0/ /sup 36/cm/sup 3//sec with T/sub +/ = T/sub g/ = 80K. This trimer ion exhibits a dependence on electron temperature similar to that predicted and measured for diatomic ions but a larger (> 10/sup -6/cm/sup 3//sec) room temperature rate coefficient. Admixtures of approx. = 1 mTorr of H/sub 2/ in 20 Torr of neon at 265K lead to an H/sub 3//sup +/ dominated afterglow. The recombination coefficient, ..cap alpha..(H/sub 3//sup +/) varies little over the range 256 less than or equal to T/sub e/ < approx. = 400K, then approaches a T/sub e//sup (-0/88)/ variation, i.e., ..cap alpha..(H/sub 3//sup +/) = (2.0 +/- 0.3) x 10/sup -7/((T/sub e/)/(300))/sup -0/ /sup 88/ cm/sup 3//sec for approx. = 400K
Research Organization:
Pittsburgh Univ., PA (USA)
OSTI ID:
5013740
Country of Publication:
United States
Language:
English