We present preliminary results of a full quantum calculation of state to state cross sections for H on H2. These cross sections are calculated for v=0,4 j=0,15 for energies up to 3.0 eV. The cross sections are calculated on the BKMP2 potential surface (Boothroyd et al. 1996) with the ABC scattering code (Skouteris et al. 2000)

Archer, D.

Balakrishnan, N.

Lepp, S. H.

NASA Technical Reports Server

NASA LAW, February 14-16, 2006, UNLV, Las Vegas
Astrochemistry in the Early Universe: Collisional Rates for H on
H2
S. H. Lepp & D. Archer
Physics Dept., University of Nevada, Las Vegas, NV 89154
N. Balakrishnan
Chemistry Dept., University of Nevada, Las Vegas, NV 89154
ABSTRACT
We present preliminary results of a full quantum calculation of state to state
cross sections for H on H2. These cross sections are calculated for v=0,4 j=0,15 for
energies up to 3.0 eV. The cross sections are calculated on the BKMP2 potential
surface (Boothroyd et al. 1996) with the ABC scattering code (Skouteris et al.
2000).
1. Introduction
The chemistry of the early universe is dominated by hydrogen. The standard big bang
model produces only hydrogen, helium and trace amounts of lithium. These elements must
makeup the gas that forms the first compact objects and cooling from these allows these first
objects to form. A comprehensive model of the chemistry has been developed in Stancil,
Lepp and Dalgarno (1996, 1998, 2002).
As part of that project we started calculations to get improved cooling curves for H2,
we found a large difference in H on H2 collision rates. There was good agreement within the
ground vibrational state, but excited state transitions could differ by orders of magnitude.
See figures below.
Our calculations were done using the ABC program by Skoteris, Castillo, and Manolopou-
los(2000). We have modified it to use the potential surface of Boothroyd, Keogh, Martin,and
Peterson (1996). The ABC program uses the coupled-channel hyperspherical coordinate
method to solve the Schrodinger equationfor three nuclei on a single Born-Oppenheimer po-
tential energy surface. The program was run for a grid of energies up to 3.5 eV, so that we
can calculate state to state rates for v=0-5, j=0-15.
https://ntrs.nasa.gov/search.jsp?R=20060052418 2019-08-29T18:47:27+00:00Z
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2. Results
To compare with Sun and Dalgarno (1994) we ran some calculations on the DMBE
potential surface (Varandas 1987). The results from the ABC code agree well with the
earlier Sun and Dalgarno (1987) results as can be seen in Figure 1.
Fig. 1.— The cross section for the lowest two transitions for SD (Sun and Dalgarno 1987)
and ABC (this calculation).
We have completed the calculations for the state-state cross sections on the BKMP
surface (Boothroyd et al 1996) and will soon publish them (Archer 2006). These will be the
first complete study of the state-state rates for H on H2 for lower levels.
This work is based upon work supported by the Department of Energy under Award
Number DE-FG36-05G085028.
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REFERENCES
Archer, David, 2006 Ph.D Thesis.
A.I. Boothroyd, W.J. Keogh, P.G. Martin and M.R. Peterson, 1996 J. Chem. Phys., 104,
7139.
Stancil, P. C., Lepp, S., & Dalgarno, A. 1996, ApJ, 458, 401
Stancil, P. C., Lepp, S., & Dalgarno, A. 1998, ApJ, 458, 401.
Lepp, S., Stancil, P.C. and Dalgarno, A. 2002 J. Phys. B, 35, R57.
Skouteris, D., Castillo, J. F. and Manolopoulos, D. E. 2000, Comput. Phys. Commun. 133,
128.
Sun, Y. and Dalganro A. 1994 ApJ, 427, 1053.
Varandas, A.J.C., Brown, F.B., Mead, C.A., Truhlar, D.G. and Blaise, N.G. 1987, J Chem.
Phys. 90,300.


Astrochemistry in the Early Universe: Collisional Rates for H on H2

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