Adiabatic ionization energy and electron affinity of CH2Br

The photoionization efficiency spectrum of supersonically cooled CH2Br has been measured near its ionization threshold. The adiabatic ionization energy (IE) of CH2Br is determined to be 8.61±0.01 eV, in excellent agreement with the value obtained previously using the He i photoelectron spectroscopic method. We have also performed Gaussian-2 (G2) calculations on CH2Br+, CH2Br, and CH2Br− which yield values of 8.47 and 0.97 eV for the IE and electron affinity of CH2Br, respectively. The G2 electron affinity is in accord with the literature value of 1.0±0.3 eV calculated from the acidity of CH3Br.