Autoionization-Detected Infrared Spectroscopy of Jet-Cooled Naphthol Cations

Abstract

We applied autoionization-detected infrared (ADIR) spectroscopy in order to observe OH stretching vibrations of jet-cooled 1-and 2-naphthol cations. In this technique, high Rydberg states, the vibrational levels of which are essentially the same as those of the corresponding bare molecular ion, were prepared by two-color doubleresonance excitation. Vibrational transitions in the ion core of the high Rydberg states were measured by detecting the vibrational autoionization signal. For rotational and structural isomers of naphthol, similar lowfrequency shifts of the OH frequencies upon ionization were found. The OH frequency shifts of naphthols were much smaller than that found for phenol, although both molecules have quite similar OH frequencies in their neutral ground state. This remarkable difference in frequency shifts was qualitatively explained in terms of the charge delocalization in the aromatic ring. In addition, the OH stretching vibrations of the 1-and 2-naphthol-Ar cluster cations were observed by infrared photodissociation spectroscopy. It was found that perturbations from the Ar atom to the hydroxyl group of naphthol are negligible in both the neutral and cationic ground states.

Infrared spectroscopy of the phenol-N2 cluster in S and D: Direct evidence of the in-plane structure of the cluster

“…Similar negligible frequency shifts are also known for the in-plane vibrations of other aromatic-Ar cluster cations, such as p-ethylphenol for the CH stretches 15 and 2-naphthol for the OH stretch. 16 On the other hand, the large OH frequency shift in the phenol-N 2 cation is an unequivocal evidence for the in-plane structure, in which phenolic OH is bound to the lone pair of electrons of N 2 . This is consistent with the ab initio calculations for the cationic state and the ZEKE photoelectron study by Haines et al 5 The drastic increase of the frequency shift demonstrates a significant enhancement of the intermolecular bond strength between phenol and N 2 upon the ionization, and the hydrogen bond nature of the intermolecular bond is clear in the cation.…”

Structures of Carbazole−(H2O)n (n = 1−3) Clusters Studied by IR Dip Spectroscopy and a Quantum Chemical Calculation

“…This method is a kind of population labeling spectroscopy, and has been applied to clusters to extract the electronic transitions due to a single species. 22,[37][38][39][40][41][42]49 Here, the IR laser frequency is fixed to the carbazole NH stretch at 3390 and 3305 cm -1 for carbazole-(H 2 O) 2,3 , respectively, while the UV laser is scanned over the energy range for the S 1 -S 0 transition.…”

Infrared photodissociation spectra of the C–H stretch vibrations of C6H6+–Ar, C6H6+–N2, and C6H6+–(CH4)1–4

“…Rg atoms are convenient ligands, as the weak intermolecular interaction usually causes only minor perturbations of the X ϩ chromophore. To reveal the spectrum of aromatic cations, often their complexes with Ar are investigated, 5-8 as the intermolecular interaction is weak enough to cause only small perturbations of the bare cations, 5,9 but strong enough to allow for sufficient production of X ϩ -Ar dimers, in most cases achieved by soft resonant multiphoton ionization of the neutral complex in molecular beams. Indeed, for aromatic cations, the vibrational IR spectra of X ϩ -Ar dimers appear to closely resemble those of the bare aromatic cations.…”

“…Indeed, for aromatic cations, the vibrational IR spectra of X ϩ -Ar dimers appear to closely resemble those of the bare aromatic cations. [5][6][7]10 In the case of electronic transitions, additivity rules can be used to obtain the spectrum of X ϩ from X ϩ -Rg n by extrapolation of n→0. 9 This approach has been used to predict the electronic spectrum of the phenantrene cation from the spectra of its complexes with one and two Ar ligands.…”