Infrared multiphoton dissociation

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Infrared multiphoton dissociation
Acronym IRMPD
Other techniques
Related Blackbody infrared radiative dissociation
Electron capture dissociation
Collision-induced dissociation

Infrared multiphoton dissociation (IRMPD) is a technique used in mass spectrometry to fragment molecules in the gas phase usually for structural analysis of the original (parent) molecule.[1]

How it works[edit]

An infrared laser is directed through a window into the vacuum of the mass spectrometer where the ions are. The mechanism of fragmentation involves the absorption by a given ion of multiple infrared photons. The parent ion becomes excited into more energetic vibrational states until a bond(s) is broken resulting in gas phase fragments of the parent ion. In the case of powerful laser pulses, the dissociation proceeds via inner-valence ionization of electrons.[2][3]

IRMPD is most often used in Fourier transform ion cyclotron resonance mass spectrometry.[4]

IRMPD spectroscopy[edit]

By applying intense tunable IR lasers, like IR-OPOs or IR free electron lasers, the wavelength dependence of the IRMPD yield can be studied.[5] This IRMPD spectroscopy allows for the measurement of vibrational spectra of (unstable) species that can only be prepared in the gas phase. Such species include molecular ions but also neutral species like metal clusters that can be gently ionized after interaction with the IR light for their mass spectrometric detection.[6]

See also[edit]


  1. ^ Little DP, Speir JP, Senko MW, O'Connor PB, McLafferty FW (1994). "Infrared multiphoton dissociation of large multiply charged ions for biomolecule sequencing". Anal. Chem. 66 (18): 2809–15. doi:10.1021/ac00090a004. PMID 7526742. 
  2. ^ Talebpour; et al. (1999). "Multiphoton ionization of inner-valence electrons and fragmentation of ethylene in an intense Ti:sapphire laser pulse". Chemical Physics Letters 313 (5-6): 789–794. Bibcode:1999CPL...313..789T. doi:10.1016/s0009-2614(99)01075-1. 
  3. ^ Talebpour; et al. (2000). "Dissociative ionization of benzene in intense ultra-fast laser pulses". J. Phys. B: At. Mol. Opt. Phys. 33 (21): 4615–4626. Bibcode:2000JPhB...33.4615T. doi:10.1088/0953-4075/33/21/307. 
  4. ^ Laskin J, Futrell JH (2005). "Activation of large ions in FT-ICR mass spectrometry". Mass spectrometry reviews 24 (2): 135–67. doi:10.1002/mas.20012. PMID 15389858. 
  5. ^ Polfer, Nick C.; Oomens, J (2007). "Reaction products in mass spectrometry elucidated with infrared spectroscopy". Physical Chemistry Chemical Physics 9 (29): 3804–17. Bibcode:2007PCCP....9.3804P. doi:10.1039/b702993b. PMID 17637973. 
  6. ^ Gruene P, Rayner DM, Redlich B, van der Meer AF, Lyon JT, Meijer G, Fielicke A (2008). "Structures of Neutral Au7, Au19, and Au20 Clusters in the Gas Phase". Science 321 (5889): 674–6. Bibcode:2008Sci...321..674G. doi:10.1126/science.1161166. PMID 18669858.