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number of vibrational states is present before dissociation occurs, in contrast to ionization where an infinite number of levels lies below the ionization limit (51). The upper limit v in (5.26) is the largest integer for which E < D , where D  is the measured value of the dissociv     e         e

ation energy.

        2. Atomic ionization H t H+ + e.--The equilibrium particle densities of the atomic ionization reaction are related by the Saha equation


          NH+ Ne    2   + 2e m k 3/2      -EH/kT
            N       2   -u          T'/2 e         (5.27)


where EH is the ionization potential of atomic hydrogen. The partition function of the hydrogen ion is


                         uH+ = 1                   (5.28)


since ionized atomic hydrogen has only one state. The partition function of atomic hydrogen is given by (5.7).

        3. Atomic electron attachment H- Z H + e.--The Saha equation relating the particle densities of the attachment reaction is

          NH N      uH   2'lm k 3/2
          H e = 2 H         e k ) T3/2 e-EB-/kT    (5.29)
          N H-      uH-   h2


where EH- is the ionization energy of the negative