Electric dipole moment and hyperfine properties of bromoacetylene in the ground and first excited C-H stretching vibrational states

Molecular beam electric resonance spectroscopy, combined with color center laser excitation, has been used to measure the electric dipole moment and Br hyperfine properties of bromoacetylene in its ground and first excited C-H stretching vibrational states. For the HCC⁷⁹Br, v = 0: μ = 0.229 62(1) D, eQq = 648.113(3) MHz, C_Br = 6.4(3) kHz, and B = 4000.07 MHz. For the HCC⁷⁹Br, v = 1: μ = 0.248 82(1) D, eQq = 648.160(2) MHz, C_Br = 7.0(3) kHz, and B = 3992.79 MHz. For the HCC⁸¹Br, v = 0: μ = 0.229 56(1) D, eQq = 541.430(1) MHz, C_Br = 7.4(1) kHz, and B = 3978.46 MHz. For the HCC⁸¹Br, v = 1: μ = 0.248 61(1) D, eQq = 541.464(3) MHz, C_Br = 7.6(4) kHz, and B = 3971.34 MHz. The vibrational band origin for the C-H stretching vibration is 3367.7(2) cm ^-1.