Infrared multiphoton dissociation spectroscopy

Armentrout, RB. Rodgers, M.T. Oomens, J. SteUl, J.D. Infrared multiphoton dissociation spectroscopy of cationized serine Effects of alkah-metal cation size on gas-phase conformation. J. Phys. Chem. A 2008,112, 2248-2257. 

Lucas, B. Gregoire, G. Lemaire, J. Maitre, R Glotin, F. Scheimann, J.R Desfrancois, C. Infrared multiphoton dissociation spectroscopy of protonated N-acetyl-alanine and alanyl-histidine. Int. J. Mass Spectrom. 2005, 243, 105-113. 

Asvany, O. Kumar, P Redlich, B. Hegemann, I. Schlemmer, S. Marx, D. Understanding the infrared spectrum of bare CH5-I-. Science 2005, 309, 1219-1222. Gregoire, G. Gaigeot, M.P Marinica, D.C. Lemaire, J. Schermann, J.P Desfrancois, C. Resonant infrared multiphoton dissociation spectroscopy of gas-phase protonated peptides. Experiments and Car-Parrinello dynamics at 300 K. Phys. Chem. Chem.Phys. 2007, 9, 3082-3097. 

Lucas B, Gregoire G, Lemaire J, Maitre P, Ortega JM, Rupenyan A, Reimann B, Schermann JP, Desfrancois C (2004) Investigation of the protonation site in the dialanine peptide by infrared multiphoton dissociation spectroscopy. PCCP 6 2659-2663... 

Schmidt J, Meyer MM, Spector I, Kass SR (2011) Infrared multiphoton dissociation spectroscopy study of protonated p-aminobenzoic acid does electrospray ionization afford the amino- or carboxy-protonated ion J Phys Chem A 115 7625-7632... 

A secondary a-deuterium KIE of 0.95, an 0 tracer study, infrared multiphoton dissociation and NMR spectroscopy, a kinetic study, a trapping experiment, and B3LYP/6-311-l-G(2d,p) calculations have shown that the base-catalysed conversion of (5)-(l(3//)-isobenzofuranon-3-yl)isothiuronium bromide into A,A -dimethyl-lV-3-oxo-l,3-dihydro-2-benzofuran-l-yl)thiourea occurs by the double 5 2 displacement mechanism shown in Scheme 8. ... 

Infrared MultiPhoton Dissociation (IRMPD) spectroscopy coupled to ElectroSpray Ionization (ESI) sources have also been applied to CBHs [60-66]. So far, the study of CBHs by ESI has focused on relatively simple mono- or disaccharides bound to metal atoms carrying the charge. This is because stabilizing the protonated forms of non-substituted carbohydrates with this ionization technique is difficult, although probably not impossible. However, it has recently been possible to observe the formation of a protonated monosaccharide (aMeGal-H" ) produced by UV photo-ionization of phenol bound to the CBH within a molecular complex [67]. 

When treating ion spectroscopy one should not forget anions. Similar spectroscopic techniques may be used as for cation spectroscopy. For instance dissociation spectroscopy is also possible for molecular anions. Since excited anionic electronic states mostly do not exist, one uses infrared multiphoton dissociation to study vibrational levels of the ground state. Another interesting technique is the photoelectron spectroscopy of anions (photodetachment photoelectron spectroscopy), which exhibit a very specific feature. This technique differs from cation <— neutral photoelectron spectroscopy in two respects (i) the final state is a neutral one thus anion photoelectron spectroscopy delivers information about neutrals rather than ionic systems, (ii) The initial state is anionic thus mass selection before spectroscopy is possible. As a result, mass selective spectroscopic information of neutral molecular systems is supplied which otherwise is not accessible. This is of particular interest for neutral systems which are only available in complex mixtures or are short-lived intermediate reaction products or radicals. 

The method discussed here is photofragmentation translational spectroscopy. In this method, the molecule of interest is expanded frcMn a nozzle into a vacuum, and then the expansion is collimated to form a molecular beam. The molecular beam is then crossed with the output of a pulsed CO2 laser which excites the molecule of interest above the dissoda-tion threshold, relying on infrared multiphoton excitation to induce decomposition. In order to dissociate, a molecule must absorb approximately 20 infrared photons. 

---