Isotopomer selective infrared predissociation spectroscopy of charged water clusters T. L. Guasco, B. M. Elliott, M. Z. Kamrath and M. A. Johnson
Predissociation Dip Spectroscopy Reflectron Coaxial TOF Detector ± 1. 5 ke. V Time of Flight, ms probe fragment Signal pump fragment hnprobe (fixed) hnpump (scanned)
Predissociation Yield H 2 DO+ · Ar 2200 2400 2600 2800 3000 3200 Photon Energy, cm-1 3400 3600 3800
Isomers of H 2 DO+ · Ar 2400 2600 2800 3000 3200 3400 3600 3800
H 5 O 2+ · RG nsp na H H O H + O H Predissociation Yield B) H 5 O 2+ · Ne H H ns H O H + O H H O 1500 + O H A) H 5 O 2+ · Ar 1000 H H Ar 2000 Photon Energy, 2500 cm-1 3000 3500
H 4 DO 2+ · Ar experimental shared D Ar end Ar-bound Free end 2400 2500 2600 2700 2800 3400 3500 3600 3700 3800
Predissociation Yield H 4 DO 2+ · Ar 800 1200 1600 2400 2800 Photon Energy, cm-1 3200 3600
3500 3600 3700 Photon Energy, cm-1 3800
Predissociation Yield 800 1200 1600 2400 2800 -1 Photon Energy, cm 3200 3600
(H 2 O)n¯ HOH bending region Bare water (H 2 O)4 ¯· Ar 6 Sharp feature red-shifted relative to bare water molecule 1400 1500 1600 1700 Photon Energy, cm-1 1800
Calculated Intensity (H 2 O)4–·Ar 6 (D 2 O)4–·Ar 6 OD stretch H 2 O bend // D C AA Double acceptor or “AA” water molecule contacts electron cloud Predissociation Yield // B A 1400 1500 1600 1700 1800 // 2400 2500 2600 2700 2800 Photon Energy, cm-1
(H 2 O)7¯ · Arn II I I' n= 10 Isomer I 8 6 5 Isomer I' 4 2 Isomer II 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 Electron Binding Energy (e. V) 1. 6
(H 2 O)7¯ · Arn AA Isomer I' * Isomer II 1600 3200 Photon Energy, cm-1 3400
(H 2 O)6¯ · D 2 O · Arn (H 2 O)7 - A) (H 2 O)6 -·Ar (H 2 O)6 - Relative Ion Intensity (H 2 O)7 -·Ar (H 2 O)3 -·Ar B) D 2 O·(H 2 O)6 - * 50 55 60 TOF (msec) * * 65 70
(H 2 O)6¯ · D 2 O · Arn AA * HOD AA 1000 1200 1400 1600 2400 2600 2800 3000 3200 3400 3600 3800 Photon Energy, cm-1
Isomer Selective Spectroscopy of OD stretches Associated with AA water (H 2 O)6¯ · D 2 O · Arn By probing OD bands we are able to definitively isolate the contributions from a single water molecule 2400 2500 2600 2700 Photon Energy, cm-1 2800
Isomer Selective Spectroscopy of OD Stretches Associated with Scaffold Water Molecules of (H 2 O)6¯ · D 2 O · Arn By probing OD bands we are able to definitively isolate the contributions from a single water molecule 2400 2500 2600 2700 Photon Energy, cm-1 2800
(H 2 O)6¯ · D 2 O · Ar 5 Double Resonance Results Pump: 2400 – 2800 cm-1 Probe: 1138 cm-1 (AA DOD Bend) 1000 1200 1400 1600 1800 2400 2600 Photon Energy, cm-1 2800
Conclusions • Successful extension of isomer selective infrared predissociation technique to isotopomers • Isolation of isomers with significant spectral overlap in H 4 DO 2+· Ar • Verification of bands associated with “AA” water in (H 2 O)n¯
Acknowledgments