5314027778

POSTER SESSION. H36

HIGH RESOLUTION IIWESTIGATION ON THE t/₃ BAND OF

CH³⁵C1₃

.1. PIETILA, V.-M. HORNEMAN and R. ANTTILA. Department of Physical Sciences, (Jniversity 0} Oulu, 90570 Oulu, Finland.

The parallel fundamental band v₃ of chloroform has been measured with the aid of the Brukcr IFS 120 HR Fourier spectroincter in Oulu. The maximum path difference corre-sponding to a theoretical linewidth beiow 0.0009 cm”¹ was used. The detector was a liquid helium cooled Si-bolometer. The total ineasurement time was 58 hours. The absorption path length and pressure were 41.6 m and 1.5 Torr, respectively. The isotopically pure sainple was synthesized in prof. Burger’s laboratory in Wuppertal. The sample was the same as in our recently published study of the 1/2 band°, but now the new celi⁶ was used in the measurements.

The 1/3 band appeared as an unpcrturbed parallel band covering the region 345-390 cm^-1. In the R(J) and P(J) transitions the Iow K components formed unresolved peaks and the K structure could be resolved starting from K = 12 onwards. Morę than 5000 Rk(J) and Pk(J) Hnes could be assigned. The maximum J and K values were 113 and 83, respectively. About 1500 ground State combination differences were formed and fitted. The ground State constants so received arę in excellent agreement with the morę accurate millimeterwave results of Gaz7X)li et al ^c. By constraining the ground State constants the following preliminary results were obtained (no AH was free):

i/₀    367.295554(8) cm"¹    D'j - D'j    -5.54(6) x 10^-11 cm'¹

B' - U"    -7.7056(4) x 10'⁵ cm"' D'_jk - D"_jk 1.56(2) x 10'¹⁰ cm'¹

C' - C" - (B' - B") 5.8445(7) x 10"⁵ cm"¹    D‘_k-D '_k    -8.5(2) x lO’¹¹ cm*¹

In addition to the main w₃ band also peaks belonging to different hot bands and correspond-ing to the unresolved Iow K components were observed and assigned. Thus information about the bands 2i^ - u3, 31/3 - 2^, v₃ -t-1^6 — ^6 and 2u₃ + v+ could be deducecL

“R Paso, V.-M. Horneman, .1. Pietila, and R. Anttila, Chem. Phys. Lett. 247, 277 282 (1995)

^frT. Ahonkn, P. Karmu, and V.-M. Horneman, Fifteenth Colloquium on High Resolution Molecnlar Spect.roscopy, Glasgow, Scptember 7 11, 1997, contribution M4

^eG. Gaz/.oi.i. G. Gotti, and L. Dore, Chem. Phys. Lett. 203, 227 231 (1993)