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For center-of-mass electron energies ^0,08 eV (~ 1000 K) nearly all electron-ion dissociative recombination cross sections thus far measured by us follow the E~x dependence predicted by theory. This corresponds to a T e "°°5 temperature dependence of the reaction-rate coefficient.In the literature there is general agreement between theory 1 and experiment 293 as to the magnitude of electron-molecular-ion dissociative-recombination cross sections for many diatomic and polyatomic ions. However, one of the most perplexing experimental problems that has remained has been the lack of agreement between the measured energy dependences of recombination cross sections (rate coefficients) particularly for electron energies below 0.1 eV (T e < 1200 K). Theory maintains 1 ' 4 that ani?" 1 power law for a vsE holds at lower center-of-mass electron energies while many of the experiments fail to give support to this dependence. 2 In this report we present evidence for anE" 1 dependence of the cross section which dominates all dissociativerecombination cross sections thus far examined by us at electron energies through the interval -0.01 and ^0.08 eV.Recent experiments in our laboratory 3 have confirmed that for H 2 + and H 3 + both "direct" and "indirect" recombination processes are important in the energy interval below ~ 2 eV. By "direct" we mean the process where a bound-ionplus-electron potential energy surface intercepts or nearly intercepts a surface for an unbound molecule. The electrons and ion enter on one surface while the dissociative products separate on the other. By "indirect" we signify those processes where Rydberg coupling between the electronic, vibronic, and rotational states of the electron-ion system and a bound Rydberg state leads to the formation of an intermediate excited neutral molecule. This bound Rydberg or intermediate compound state is then free to either autoionize or predissociate. For a more complete review of these processes, refer to Bardsley and Biondi. 2 In our previous papers, we have described the merged electron-ion beam apparatus used in our studies and have utilized the high-energy resolution characteristic of this experimental approach to show that, at least above -0.08 eV, autoionization of the temporarily formed (e-B. 2 + ) and (e-H 3 + ) compound states competes effectively with direct dissociative recombination and predissociation, thus leading to a structure-filled cross-section curve. Furthermore, we have shown for H 2 + that the state of vibrational excitation and for CH + electronic excitation of the ion entering into recombination can have a substantial effect upon the magnitude of the measured cross section and upon the position and magnitude of the structure in the curve if not upon the general shape of the curve. 3 The importance and control of the excitation will be described more completely in later papers.Since our initial high-re solution studies we have focused our total attention upon gathering lowerresolution cross-section data needed for fusion, astrophysical, an...

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