Threshold photoelectron spectroscopy of iminoborane, HBNH

We report the mass-selected threshold photoelectron spectrum (ms-TPES) of iminoborane (HBNH), generated by pyrolysis of borazine. The adiabatic ionization energy (IE) of the X^{+ 2}Π ← X ¹Σ⁺ transition was determined to be 11.31 ± 0.02 eV and the wavenumber of the B–N stretching vibration in the cation was measured to be 1550 cm⁻¹. The Renner–Teller splitting in the X^{+ 2}Π state gives rise to two sets of vibrational progressions, separated by 70 meV.