Hot bands of acetylene in the 3 mu m region

The high-resolution FTIR spectrum of acetylene in the 3 mu m region has' be en analysed for various hot bands terminating on upper stretch-bend combina tion levels corresponding to multiple excitation of the bending modes. The data have been fitted to obtain effective parameters, including rotational l-type doubling constants for the upper states. Molecular parameters for th e 'missing' Pi level arising from vibrational l-type doubling of the (v(2)2v(4)+v(5))and (v(2)+v(4)+2v(5)) states are reported for the first time.