Data processing for structure allocation of molecular C2HD

Acetylene (C2H2) is a linear quadratic molecule and an example of C - C with triple band in chemistry that The structure of acetylene molecule has 7 normal vibrational modes. Rovibrational absorption spectrum in the IR region of this molecule is detected in the outer atmosphere of the earth. It plays an important role in intermolecular studies. this molecular is include two important iso toper 12C2,HD12C2D2 that in this paper we study on l000cm-1 to l0000cm-1 for the isotope C2HD. Energy expansion coefficients for series of stretch vibration bands of some combination tones is calculated and approximated. At the end, the study of prediction of intensity and comparison to experimental intensity is done too In this paper we try to describe our experimental or theoretical results.