The Interactingv6= 2 Levels of D3Si35Cl: A Tool to Determine Ground State Constants from High-Resolution Spectra in the 440–590 and 900–1100 cm−1Regions

Abstract High-resolution FTIR spectra of monoisotopic D 3 Si 35 Cl have been recorded in the regions 440–590 cm −1 (ν 3 /ν 6 ) and 900–1100 cm −1 (2ν 6 /ν 3 + ν 6 /2ν 3 ). A detailed rovibrational study was done for the 2ν 0 6 , 2ν ∓2 6 , and 2ν 3 overtone bands and for the 2ν ±2 6 –ν ±1 6 , 2ν 0 6 –ν ∓1 6 , and (ν 3 + ν ±1 6 )–ν ±1 6 hot bands. For the first time the interactions occurring between the v 6 = 2, v 3 = v 6 = 1, and v 3 = 2 levels of any trideuterated silyl halide have been analyzed. The (ν 3 + ν ±1 6 )–ν ±1 6 hot band served to obtain accurate energies of the v 3 = v 6 = 1 level, the ν 3 + ν 6 combination band not being detectable on our spectra. The first experimental determination of A 0 and D 0 K for this molecule was undertaken by a well-established method, using the ν 6 , 2ν ±2 6 –ν ±1 6 , and 2ν ∓2 6 bands. Ground state energy differences Δ K ( J ) = E 0 ( J , K ) − E 0 ( J , K − 3) were calculated for K values from 2 to 16. By a least-squares fit of 163 such differences, the A 0 and D 0 K values thus obtained were (in cm −1 ): A 0 = 1.4278230(8) and D 0 K = 5.3916(31) × 10 −6 .