Isotopomer selective infrared predissociation spectroscopy of charged water

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