Communication: He-tagged vibrational spectra of the SarGlyH{sup +} and H{sup +}(H{sub 2}O){sub 2,3} ions: Quantifying tag effects in cryogenic ion vibrational predissociation (CIVP) spectroscopy
- Sterling Chemistry Laboratory, Yale University, 225 Prospect St., New Haven, Connecticut 06520 (United States)
- Department of Chemistry and Biochemistry, Fairfield University, 1073 North Benson Rd., Fairfield, Connecticut 06824 (United States)
To assess the degree to which more perturbative, but widely used “tag” species (Ar, H{sub 2}, Ne) affect the intrinsic band patterns of the isolated ions, we describe the extension of mass-selective, cryogenic ion vibrational spectroscopy to the very weakly interacting helium complexes of three archetypal ions: the dipeptide SarGlyH{sup +} and the small protonated water clusters: H{sup +}(H{sub 2}O){sub 2,3}, including the H{sub 5}O{sub 2}{sup +} “Zundel” ion. He adducts were generated in a 4.5 K octopole ion trap interfaced to a double-focusing, tandem time-of-flight photofragmentation mass spectrometer to record mass-selected vibrational predissociation spectra. The H{sub 2} tag-induced shift (relative to that by He) on the tag-bound NH stretch of the SarGlyH{sup +} spectrum is quite small (12 cm{sup −1}), while the effect on the floppy H{sub 5}O{sub 2}{sup +} ion is more dramatic (125 cm{sup −1}) in going from Ar (or H{sub 2}) to Ne. The shifts from Ne to He, on the other hand, while quantitatively significant (maximum of 10 cm{sup −1}), display the same basic H{sub 5}O{sub 2}{sup +} band structure, indicating that the He-tagged H{sub 5}O{sub 2}{sup +} spectrum accurately represents the delocalized nature of the vibrational zero-point level. Interestingly, the He-tagged spectrum of H{sup +}(H{sub 2}O){sub 3} reveals the location of the non-bonded OH group on the central H{sub 3}O{sup +} ion to fall between the collective non-bonded OH stretches on the flanking water molecules in a position typically associated with a neutral OH group.
- OSTI ID:
- 22420110
- Journal Information:
- Journal of Chemical Physics, Vol. 140, Issue 22; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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