Spectrum of HCl

HCl shows the rotational transitions characteristic of diatomic molecules. The rotational spectrum of HCl shows some centrifugal stretching as indicated by the calculated bond length in the table.

υ cm-1 J -> J+1 R(nm) 83.03 3-4 .1288 103.73 4-5 .1288 124.3 5-6 .1289 145.03 6-7 .1289 165.51 7-8 .1290 185.86 8-9 .1291 206.38 9-10 .1292 226.5 10-11 .1293

It is typical for the frequencies υ in this range to be expressed in the units cm^-1. The transition energies in joules may be calculated from:

For high rotational transitions, the molecule must be treated as a non-rigid rotor.