  Infrared spectra of the CO2-N2 dimer are observed in the carbon dioxide nu3
asymmetric stretch region (~2350 cm-1) using a tunable infrared optical
parametric oscillator to probe a pulsed slit jet supersonic expansion. Previous
results for the b-type fundamental band are extended to higher values of Ka. An
a-type combination band involving the lowest in-plane intermolecular bending
mode is observed. This yields a value of 21.4 cm-1, and represents the first
experimental determination of an intermolecular mode for CO2-N2. This
intermolecular frequency is at odds with the value of 45.9 cm-1 obtained from a
recent 4D intermolecular potential energy surface. In addition, two weak bands
near 2337 cm-1 are assigned to the CO2 hot band transition (v1, v2, l2, v3) =
(0111) <-- (0110). They yield a value of 2.307 cm-1 for the splitting of the
degenerate CO2 nu2 bend into in-plane and out-of-plane components due to the
presence of the nearby N2. The in-plane mode lies at lower energy relative to
the out-of-plane mode.
