Chemiluminescent low·pressure flame has been found to be an excellent source to excite spectra of molecules hardly to be produced at other experimental conditions. Spectroscopic diagnostics of plasma usually employs easily resolved spectra oflight molecules such as N₂, N/, OH, CN or CH. In the present study, spectra of the a3:E+u (all u) - XI:E\ (XO\) transition of the Bi2 molecule produced in chemiluminescence from the BiJ02(al~. bl:E+) system were used to determine rotational and vibrational temperatures. Spectra were recorded using a high-resolution Fouriertransform spectrometer (Bruker IFS 120 HR) in the spectral range from 3000 to 7000 cm· l. The R, Q and P branches of the 2-3 and 6-0 bands served for the rotational temperature measurements. The vibrational temperature was derived from ~u=-3 sequence bands of the a-X transition. The both temperatures were close together and near 330 K. It indicates that for the chemiluminescent flame occurs complete rotational and vibrational relaxation.