# Rotational excitation of HCl by He (Lanza et al, 2012)

**Display rate coefficients as :**
**Display rate coefficients graphically :**
**Data information :**
- HCl initial level labelled from 2 to 11
- HCl final level labelled from 1 to 10
- He initial level labelled from 1 to 1
- He final level labelled from 1 to 1
- 8 temperatures between 10 K and 300 K
- Units : cm
^{3} s^{-1}

N/A

Reduced Mass = 3.6067 a.m.u.

### References :

None

Three 3D surfaces were calculated, using the CCSD(T) level of theory, with aug-cc-pVTZ, aug-cc-pVQZ and aug-cc-pV5Z basis sets. These calculations were performed at 43 fixed intermolecular distances, R, in the range 2.5-50 a

_{0}; and at 5 HCl intramolecular distances, i.e. 2.00, 2.25, 2.41, 2.70 and 3.10 a

_{0}. The angular dependence was described along 19 angles, for a total of 4085 ab initio points. The basis set superposition error (BSSE) was corrected at all geometries with the Boys and Bernardi counterpoise procedure (Boys and Bernardi 1970). The interaction energy in the complete basis set (CBS) limit, E

_{CBS}, was then recovered from these 3 PES, by inverting the system (Peterson et al, 1994 ; Feller & Sordo, 2000):

; with X = 3,4 or 5. Mid-bond functions were omitted from the CCSD(T) calculations due to the subsequent CBS extrapolation.

The 3D PES was fitted according to the expansion proposed by Werner et al., 1989. The fitting procedure was found to provide a good representation of the ab initio points, with differences inferior to 1% on the whole grid (i.e. with an agreement better than ~0.3 cm

^{-1} at the global minimum located at R ~ 6.3 a

_{0}). The 2D PES used in the dynamical treatment was then obtained by setting the HCl intramolecular distance to its value averaged over the fundamental vibration mode, i.e. r

_{HCl} = 2.43 a

_{0}.

### References :

- Feller D., Sordo J. A.. A CCSDT study of the effects of higher order correlation on spectroscopic constants. I. First row diatomic hydrides J. Chem. Phys. vol112 : 13 : p5604-5610, 2000
- Peterson K. A., Woon D.~E., Dunning Jr. T.~H..

Benchmark calculations with correlated molecular wave functions. IV. The classical barrier height of the H+H_{2} -> H_{2}+H reaction J. Chem. Phys. vol100 : 10 : p7410-7415, 1994, May - Werner H.-J., Follmeg B., Alexander M.~H., Lemoine D.. Quantum scattering studies of electronically inelastic collisions of CN (X2\Sigma
^{+},A2\Pi) with He J. Chem. Phys. vol91 : 9 : p5425-5439, 1989, November - Boys S.~F., Bernardi F.. The calculation of small molecular interactions by the differences of separate total energies. Some procedures with reduced errors. Mol. Phys. vol19 : p553--566, 1970, October

Close-coupling (CC) calculations are performed for total energies E

_{T} < 3000 cm

^{-1}. The parameters of the integrator were adjusted to insure a good covergence for the highest cross sections, i.e. with an accuracy better than 0.001

^{2} for inelastic transitions.

### References :

None

0.2 to 3000 cm^{-1}

The number of HCl rotational states was adjusted to ensure convergence and include at least 4 closed rotational levels.

Better than a few % for the current PES.

## Presentation

De-excitation rate coefficients are provided for the first 11 rotational levels of HCl (up to j=10) in collision with He, for temperatures between 10K and 300K.

## References

* NB : the main reference is displayed in red*
**PDF Version**
## Collision history

**Status** |
**Version** |
**Date** |

Collision added into the database |
1 |
2016-02-09 |

Documentation modified |
2 |
2016-02-26 |