Ammonia Borane, NH₃BH₃: A Threshold Photoelectron–Photoion Coincidence Study of a Potential Hydrogen‐Storage Material

Abstract

We have investigated the photoionization of ammonia borane (AB) and determined adiabatic ionization energy to be 9.26 � 0.03 eV for the X + 2 E ! X 1 A 1 transition. Although the threshold photoelectron spectrum appears at first glance to be similar to the one of the isosteric ethane, the electronic situation differs markedly, due to different orbital energies. In addition, an appearance energy AE 0K -(NH 3 BH 3 , NH 3 BH 2 + ) = 10.00 � 0.03 eV has been determined, corresponding to the loss of a hydrogen atom at the BH 3 -site. From the data, a 0 K bond dissociation energy for the BÀ H bond in the cation of 71.5 � 3 kJ mol À 1 was derived, whereas the one in the neutral compound has been estimated to be 419 � 10 kJ mol À 1 .

Dehydrogenation of Ammonia Borane Impacts Valence and Core Electrons: A Photoemission Spectroscopic Study

“…This is confirmed by a measurement using photoelectron–photoion coincidence (PEPICO) spectroscopy of and AIE of 9.26 ± 0.03 eV and an VIE of 10.00 ± 0.03 eV . The present calculated VIE of AB at 10.57 eV agrees well with the measurements which are between the two experimental measurements of 10.58 eV and 10.00 eV . In addition, our recent joint XPS experimental and theory study of hydroxybenzoic acids revealed that the vibrational impact is small for fast ionization processes so that in the present study, only the first-order VIEs are considered.…”

“…It is noted that the VIE and AIE of ammonia borane (H 3 BNH 3 ) can differ by as much as approximately ∼1 eV, as the structures of the cation and neutral AB can be quite different. This is confirmed by a measurement using photoelectron–photoion coincidence (PEPICO) spectroscopy of and AIE of 9.26 ± 0.03 eV and an VIE of 10.00 ± 0.03 eV . The present calculated VIE of AB at 10.57 eV agrees well with the measurements which are between the two experimental measurements of 10.58 eV and 10.00 eV .…”

“… 52 The present calculated VIE of AB at 10.57 eV agrees well with the measurements which are between the two experimental measurements of 10.58 eV 12 and 10.00 eV. 52 In addition, our recent joint XPS experimental and theory study of hydroxybenzoic acids revealed that the vibrational impact is small for fast ionization processes 53 so that in the present study, only the first-order VIEs are considered. In addition, the fact that only the first IE available without any higher valence IEs of the boron–nitrogen hydrides also makes such high level calculations less useful.…”

“… b Experiment (MS) VIE for 10.58 eV and adiabatic ionization energy (AIE) for 9.44 eV, 12 which agree well with a recent AIE of 9.26 ± 0.03 eV and VIE of 10.00 ± 0.03 eV, using photoelectron–photoion coincidence (PEPICO) spectroscopy. 52 Theory with CCSD(T)/CBS, 9.29 eV. 6 896.4 kJ/mol (9.29 eV) 10 and 997.7 kJ/mol (10.61 eV).…”

Photoemission and X-ray Absorption Investigation of Ammonia-Borane in the Gas Phase

“…Schleier et al 2 reported that the first ionic state of AB (X state) supported vibronic structure, implying that this ionic state is bound. Here, we have shown that the A state also supports vibronic structure.…”