Microwave measurement of the α3 vibrationrotation constant of ClCN and BrCN vibrational energy transfer from active nitrogen

Vibrational energy transfer between active nitrogen N*₂, and the (0,0⁰, 1) state of ClCN and BrCN has allowed the determination of the α₃ vibrationrotation constant by microwave spectroscopy, with the values: α₃(³⁵ClCN) = 32.25 MHz, α₃(³⁷ClCN) = 31.68 MHz, α₃(⁷⁹BrCN) = 20.37 MHz and α₃(⁸¹BrCN) = 20.24 MHz. For ³⁵ClCN the α₁ vibrationrotation constant has also been determined with a standard technique, giving α₁ = 24.65 MHz. A new evaluation has been made of the equilibrium structure of ClCN as follows: r_e(CN) = 1.1606 A, r_e(CCL) = 1.6290 A.