An IR-IR double resonance technique has been applied to an argon seede
d molecular jet to perform hot band spectroscopy especially on the nu7
+ nu9 <-- nu7 transition in ethylene. After excitation of a single ro
vibrational level by a CO2 waveguide laser, rotational states in the n
u7 manifold are populated through collision induced rotational relaxat
ion. Results are combined with data obtained from saturation dip spect
roscopy in a 12 m long cell at room temperature. In total around 100 t
ransitions have been newly assigned to the nu7 + nu9 <-- nu7 band. A l
east-squares fitting has been applied to all levels of nu7 + nu9, exce
pt two isolated and perturbed levels at K(a) = 6. A good statistical a
greement has been obtained by taking into account a c-type Coriolis in
teraction with nu7 + 2nu10 + nu12, an a-type Coriolis interaction with
nu2 + 2nu6 and a c-type Coriolis interaction with nu4 + nu9. Furtherm
ore, earlier data on the nu10 + nu9 <-- nu10 hot band have been reexam
ined. The two hot band spectra have been compared to analyse the prope
nsities of different relaxational pathways.