  A spectral survey of IRC+10216 has been carried out in the range 11 to 14 um
with a spectral resolution of about 4 km s^-1. We have identified a forest of
lines in six bands of C2H2 involving the vibrational states from the ground to
3nu5 and in two bands of HCN, involving the vibrational states from the ground
up to 2nu2. Some of these transitions are observed also in H13CCH and H13CN. We
have estimated the kinetic, vibrational, and rotational temperatures, and the
abundances and column densities of C2H2 and HCN between 1 and 300 R* (1.5E16
cm) by fitting about 300 of these ro-vibrational lines. The envelope can be
divided into three regions with approximate boundaries at 0.019 arcsec (the
stellar photosphere), 0.1 arcsec (the inner dust formation zone), and 0.4
arcsec (outer dust formation zone). Most of the lines might require a large
microturbulence broadening. The derived abundances of C2H2 and HCN increase by
factors of 10 and 4, respectively, from the innermost envelope outwards. The
derived column densities for both C2H2 and HCN are 1.6E19 cm^-2. Vibrational
states up to 3000 K above ground are populated, suggesting pumping by
near-infrared radiation from the star and innermost envelope. Low rotational
levels can be considered under LTE while those with J>20-30 are not
thermalized. A few lines require special analysis to deal with effects like
overlap with lines of other molecules.
