ZEKE-PFI spectroscopy of 1:1 complexes of sodium with water and ammonia

Abstract

ZEKE-PFI (zero kinetic energy pulsed field ionization) photoelectron spectra of the Na(H 2 0), Na(D 2 0), Na(NH 3 ), and Na(ND 3 ) complexes are reported. Spectra of all four complexes were obtained by single-photon ionization, and, for the Na(NH 3 ) and Na(ND 3 ) complexes, by two-color (I+ I') photoionization as well, with the A 2 E state serving as the intermediate resonance. Improved values for the ionization energies (IE) and intermolecular vibrational frequencies of the complexes were determined. The single-photon ZEKE-PFI spectra show transitions only between states of the same vibrational symmetry, in accord with the selection rule for allowed electronic transitions. Some of the two-color ZEKE-PFI spectra, however, show strong transitions between states of different vibrational symmetry which we attribute to vibronic coupling in the intermediate state.

Near-infrared spectroscopy of LiNH3: First observation of the electronic spectrum

“…8 More extensive spectroscopic work has been carried out on small Na(NH 3 ) n complexes and the first such study was reported by Nitsch and co-workers, 9 who successfully obtained spectra for NaNH 3 . This and subsequent work by Schulz and co-workers, 10 and also by Rodham and Blake, 11 on both NaNH 3 and NaND 3 , has yielded resolved vibrational structure. Extension to larger complexes, with up to n = 6, was achieved by Brockhaus and co-workers, 12 but the spectra were broad and unresolved, unlike that of NaNH 3 .…”

Electronic spectroscopy of jet-cooled YbNH3

“…Structure in this non-totally symmetric vibration would require vibronic coupling to gain significant intensity, but such coupling has been seen previously in spectra of LiNH 3 and NaNH 3 . 8,9,11,12 However, this vibration would be characterized by relatively large isotope shifts on deuteration, which would be inconsistent with the YbNH 3 and YbND 3 spectra in Figure 2. Equally, there is no evidence for excitation of the umbrella mode, although in the case of YbNH 3 this is likely to fall outside of the scan range reported here.…”

“…10,13 Furthermore, Li(NH 3 ) n and Na(NH 3 ) n clusters undergo rapid non-radiative relaxation in the excited electronic state, rendering them all unobservable by REMPI except for n = 1. 8,9,14 Although there is no precise correlation between the electronic states of Li(NH 3 ) n /Na(NH 3 ) n and Yb(NH 3 ) n , as detailed below the strongly metal-centered nature of their low-lying electronic transitions would lead us to expect broadly similar behaviour. For all of these reasons we can confidently assign the spectrum in Figure 2 to YbNH 3 .…”

“…The same behaviour is seen for LiNH 3 and NaNH 3 for exactly the same reasons. 8,9,14 We can therefore draw upon the known electronic energy levels of Yb to construct a simple electronic structure model for YbNH 3 .…”

“…8,9 REMPI is unsuitable for larger Na(NH 3 ) n complexes because of rapid excited state decay and so spectra of these complexes, with up to n = 22, were obtained in the near-infrared region using a photodepletion technique. 10 The spectra obtained were attributed to perturbed 3p ← 3s transitions on the Na atoms and these shift strongly to the red in moving from n = 1 to n = 4, with very little change thereafter.…”