1. New Collision Data for H/H2 and CxHy Databases
R.K.Janev
Macedonian Academy of Sciences and Arts, Skopje, Macedonia

2. Scope:
Resonant vibrational excitation and dissociative attachment in e-H2 in eV region;
Mutual neutralization in slow collisions of H- with H2+ and H3+ ions;
Electron impact excitation of X→ A and X→B transitions in CH
Dissociative excitation and ionization in
e + CHy+collisions

3. RVE and DEA in e+H2 in 11-14 eV collisions
Processes:
e + H2(X1Σg+;v=0) → H2-(2Σg+) →
→ H2(X1Σg+;v) + e (RVE)
→ H- + H(n=2) (DEA)
Theoretical approach:
- Resonance theory
- Local complex potential approximation

4. Elements of calculations

5. LCA →Non-local integro-differential Eq. for ζ(R)
In the local complex potential approximation this equation becomes (after separating the angular part):

6. H2¯ energy parameters V ¯(R) : H2¯ (2Σg+) potential energy curve
Г(R) : decay width of H2¯ (2Σg+) state
Information on V ¯(R) and Г(R) from Stibbe and Tennyson (1998;J.Phys.B) with suitable extrapolations

7. RVE cross sections
Chang, 1977; Herzenberg, 1979

14. 2. Dissociative electron attachment
Equations for ζi(R) in the LCA approximation are the same as in the RVE case
Cross section:

17. 3.Mutual neutralization in slow H2+,H3+ - H- collisions
H2+(1sσg) +H-(1s2)→H2(1sσg;nλσg)+H(1s)
Radial coupling selection rule:
Overall symmetry of initial and final states in reaction a) should be the same:
→ 1,3Σg+ final states of H2
Strong radial coupling of initial (ionic) and final (covalent) states exists only for exothermic channels: → n ≤ 3
→Final H2 states: X,EF,GK,HH (singl.) , a, h, g (tripl.)

18. Schematic potential energy diagram (at large distances)

19. Theoretical model Multichannel Landau-Zener model
(probability flux accumulation along various reaction paths for a given exit channel)
Landau-Zener two-state transition probability
in the strong interaction region (around Rx)

23. H3+ + H- D3h symmetry for H3+ and H3* states
Initial state: H3+[(1sa1’)2 A1’] + H-(1s2) (i)
Final states with same symmetry as (i):
H3[(1sa1’2 nla1’)A1’] + H(1s)
Reaction exothermicity condition selects the
first four A1’ states of H3*

24. Computational method Multichannel Landau-Zener (LZ) model
LZ two-state transition probability
Asymptotically exact ionic-covalent electron exchange interaction

25. Radiative and predissociation decay of H3* states
H3*(nl;A1’)→ (intermediary state)→
… H3[(1sa1’)2(2pe’)E’]→H2(X1Σg+) + H(1s)
→3H(1s)
(Ground state of H3 is degenerate in the FC region of H3+ with two energy branches at large R; Yahn-Teller system)

28. 4. Dissociative excitation and ionization of CDy+ by e-impact
Processes:
e + CDy+ → e + I+ + neutrals (DE) (y=1-4)
e + CDy+ → 2e + I1+ +I2+ + neutrals (DI)
Recent total cross section measurements for specific ion production, σtot(DE+DI), and also σtot(DI) for D+ production;
Mesurements of total KER at a few energies
(Louvain-la-Neuve group; P.Defrance)

34. Separation of channels
Determine channel thresholds from theoretical dissociation energies and observed KER spectra
Determine cross section points by integrating the KER peaks for a given channel at the corresponding energy
Use the inverse proportionality of cross section maximum with the threshold energy
Use the absolutely measured ionization cross section for H+ production and empirical scaling rule for the linearity of DE+ and DI+ fragments with the number of D atoms in CDy+ at high energies

35. Status: For all CDy+ ions DE+ and DI+ channels have been separated
For each of the DE+ or DI+ ion production channels the neutral fragmentation sub-channels have also been separated
All the DE+ and DI+ channel cross sections have been fitted to (relatively) simple analytic fit functions

36. 5. e-impact excitation of X→A and X→B transitions of CH
Computational method:
- Born approximation for dynamics
- Ab initio calculation of dipole moments
vi-vf resolved transitions
Predissociation included
Calculations of transitions to higher states also planned

42. Bethe-Born formula

43. Contributors: R. Celiberto (Politechnico di Bari)
J. Wadehra (Wayne Univ., Detroit)
P. Defrance, J. Lecointre, et al.
(Univ. Catholique de Louvain-la-Neuve)
J.G.Wang, C.L.Liu (IAPCM, Beijing)