5 Conclusion

The IR and SMM lineschapes are needed for interpretation of the observed solar lines in the infrared and submillimetric spectrum. The present work deals with the densities below the Inglis-Teller limit, above which line dissolution is important. The common semiclassical method is problematic since it overestimates the line widths at low densities and requires an improvement. The collision rate method is an alternative method for linewidth calculations in such cases, particularly for the electron case. Within the impact or quasistatic approximation for ions, the profile can be easily obtained as soon as the electronic and/or the ionic linewidth is calculated. For this purpose electron-Hydrogen atom transition rates are provided in Tables 4 to 6.

  

Table 4: Total electron transition rates of level n at various temperatures from 1000 to 6000 K

  

Table 5: Total electron transition rates of level n at various temperatures from 7000 to 12000 K

  

Table 6: Total electron transition rates of level n at various temperatures from 13000 to 25000 K

The spectral line broadening of the lower Rydberg lines is a more complex problem when the electron density becomes greater than the Inglis-Teller limit $N_{{\rm IT}}.$ The description of a system with one or many perturbers in the Rydberg atom must be considered. Line dissolution has to be treated conveniently. In any case, even at average densities, there is always a critical electric microfield $F_{\rm c}$ - in the integration over the microfield distribution - above which, line dissolution appears (Seaton 1990). Between the impact and static approximation for ions, an intermediate region between these two approximations is expected, for which neither of the limiting approximations are valid, thus calling for an improved modelisation.

Acknowledgements

The authors would like to acknowledge Pr. H.R. Griem for fruitful suggestions on the original manuscript.