The temperature dependence of conversion of He(2$\sp3$S$\sb1$) metastable atoms to He$\sb2$(a$\sp3\Sigma\sp+\sb{\rm u}$) metastable molecules in the three-body reaction$$\rm He(2\sp3S\sb1)+2He(1\sp1S\sb0) \to He\sb2(a\sp3\Sigma\sp+\sb{u})+He(1\sp1S\sb0)$$has been investigated over the temperature range 65K-700K. This reaction is thermally activated as a consequence of a long range repulsive barrier in the He(2$\sp3$S$\sb1)$-He(1$\sp1$S$\sb0$) interaction potential. The data reveal that there are two reaction channels with distinctly different activation energies. The temperature dependence of the measured rate coefficient $\delta$(T) is accurately described by$$\rm \delta(T) = \lbrack 87.4\ T\ exp({-}750/T){+}4.1T\ exp({-}200/T)\rbrack \times 10\sp{-37}\ cm\sp{-6}sec\sp{-1}.$$The first activation energy, 750 $\pm$ 70K(63 $\pm$ 6meV), is equal to the known He(2$\sp3$S$\sb1)$-He(1$\sp1$S$\sb0$) repulsive barrier height. The second activation energy is 17 $\pm$ 2 meV.
| Identifer | oai:union.ndltd.org:RICE/oai:scholarship.rice.edu:1911/13486 |
| Date | January 1990 |
| Creators | Zhao, Xin-xin |
| Contributors | Walters, G. K. |
| Source Sets | Rice University |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | 39 p., application/pdf |
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