Vacuum Ultraviolet (VUV) photoionization of small waterclusters
Tunable vacuum ultraviolet (VUV) photoionization studies of water clusters are performed using 10-14 eV synchrotron radiation and analyzed by reflectron time-of-flight (TOF) mass spectrometry. Photoionization efficiency (PIE) curves for protonated water clusters (H{sub 2}O){sub n}H{sup +} are measured with 50 meV energy resolution. The appearance energies of a series of protonated water clusters are determined from the photoionization threshold for clusters composed of up to 79 molecules. These appearance energies represent an upper limit of the adiabatic ionization energy of the corresponding parent neutral water cluster in the supersonic molecular beam. The experimental results show a sharp drop in the appearance energy for the small neutral water clusters (from 12.62 {+-} 0.05 to 10.94 {+-} 0.06 eV, for H{sub 2}O and (H{sub 2}O){sub 4}, respectively), followed by a gradual decrease for clusters up to (H{sub 2}O){sub 23} converging to a value of 10.6 eV ({+-}0.2 eV). The dissociation energy to remove a water molecule from the corresponding neutral water cluster is derived through thermodynamic cycles utilizing the dissociation energies of protonated water clusters reported previously in the literature. The experimental results show a gradual decrease of the dissociation energy for removal of one water molecule for small neutral water clusters (3{le}n{le}9). This dissociation energy is discussed within the context of hydrogen bond breaking in a neutral water cluster.
- Research Organization:
- Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
- Sponsoring Organization:
- USDOE Director, Office of Science
- DOE Contract Number:
- AC02-05CH11231
- OSTI ID:
- 919516
- Report Number(s):
- LBNL--62671
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 40 Vol. 111; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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