The vibrational spectra of molecular ions isolated in solid neon. XIII. Ions derived from HBr and HI

Abstract

Articles you may be interested inOn the vibrational fine structure in the nearthreshold photofragmentation spectrum of the I−CH3I complex: Spectroscopic observation of nonadiabatic effects in electronmolecule scattering When a Ne:HBr or a Ne:HI sample is codeposited at approximately 5 K with discharge-excited neon atoms, the infrared spectrum of the resulting solid includes not only the absorptions of the HX molecule and its multimers but also a prominent absorption of HBr ϩ or HI ϩ . The absorption of each of the two cations lies within a few cm Ϫ1 of its gas-phase band center. The vibrational fundamentals of DBr ϩ and DI ϩ are also identified in experiments on deuterium-enriched samples. Other infrared absorptions are assigned to normal and deuterium-substituted ͑HBr͒ 2 ϩ and ͑HI͒ 2 ϩ , as well as to BrHBr Ϫ , BrDBr Ϫ , and IHI Ϫ . Studies of changes in the absorption spectrum following exposure of the deposit to filtered visible and near ultraviolet radiation support these assignments and provide further information on photodissociation and photodetachment processes occurring in these systems.

Gas phase infrared spectroscopy of cluster anions as a function of size: The effect of solvation on hydrogen-bonding in Br−⋅(HBr)1,2,3 clusters

“…The observed absorption band of BrHBr Ϫ at 1558 cm Ϫ1 is assigned to the overtone of the 3 absorption band previ- ously observed at 728 and 753 cm Ϫ1 in matrix IR studies. 8,12 The high negative anharmonicity implied by this assignment is consistent with the calculations by Del Bene and Jordan, 16 who find a substantial negative anharmonicity for the 3 mode in FHF Ϫ , ClHCl Ϫ , and BrHBr Ϫ .…”

“…Coarser scans extending from 625 to 1700 cm Ϫ1 showed no additional features, nor did finer scans from 700-800 cm Ϫ1 , where the 3 antisymmetric stretch fundamental is expected. 7,8,12,15,16,30 A constant Br Ϫ background signal resulting from collision induced dissociation of the BrHBr Ϫ parent ions is observed. The Br Ϫ background is on the order of 0.03% of the parent ion signal, and photofragmentation at 1558 cm Ϫ1 yields approximately three times the background signal.…”

“…4 Experiments and calculations indicate these anions to be symmetric, D ϱh species with two equal H-X bond lengths. [5][6][7][8][9][10][11][12][13][14][15][16] These anions and their asymmetric counterparts, such as BrHI Ϫ , are also of interest as transition state precursors in negative ion photoelectron spectroscopy experiments. 17,18 However, the very factor that causes these hydrogen bonds to be so strong, namely the extensive sharing of the H-atom between two halogen atoms, also makes these bonds highly susceptible to solvent perturbation that can, for example, destroy the symmetry of the bonds in symmetric XHX Ϫ anions.…”

“…However, for strongly hydrogen-bonded anions such as symmetric bihalides, the antisymmetric stretch ( 3 ) fundamental is considerably lower than this; gas phase IR spectroscopy of FHF Ϫ and ClHCl Ϫ yields 3 frequencies of 1331 and 723 cm Ϫ1 , respectively, 10,11 while matrix isolation spectroscopy of BrHBr Ϫ yields 3 frequencies ranging from 728 to 753 cm Ϫ1 . 8,12 Hence, the systematic study of the IR spectroscopy of bare and clustered bihalides requires a very different type of light source.…”

Aqueous Solvation of Bihalide Anions

“…Bihalide anions [1][2][3][4][5][6][7][8] XHX -are linear anions with a hydrogen atom placed between two halide atoms X. Interest in bihalide anions stems from the fact that they form strong intramolecular hydrogen bonds [7][8][9][10] and they are useful for studying transition states in the corresponding neutral species via photodetachment experiments.…”