Single photon ionization of hydrogen bonded clusters with a soft x-ray laser: (HCOOH){sub x} and (HCOOH){sub y}(H{sub 2}O){sub z}

Pure, neutral formic acid (HCOOH){sub n+1} clusters and mixed (HCOOH)/(H{sub 2}O) clusters are investigated employing time of flight mass spectroscopy and single photon ionization at 26.5 eV using a very compact, capillary discharge, soft x-ray laser. During the ionization process, neutral clusters...

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Published in:The Journal of chemical physics 2007-06, Vol.126 (24)
Main Authors: Heinbuch, S., Dong, F., Rocca, J. J., Bernstein, E. R., Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523 and NSF ERC for Extreme ultraviolet Science and Technology, Colorado State Univversity, For Collins, Colorado 80523, Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523 and NSF ERC for Extreme Ultraviolet Science and Technology, Colorado State University, Fort Collins, Colorado 80523, Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, NSF ERC for Extreme Ultraviolet Science and Technology, Colorado State University, Fort Collins, Colorado 80523
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Language:eng
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Summary:Pure, neutral formic acid (HCOOH){sub n+1} clusters and mixed (HCOOH)/(H{sub 2}O) clusters are investigated employing time of flight mass spectroscopy and single photon ionization at 26.5 eV using a very compact, capillary discharge, soft x-ray laser. During the ionization process, neutral clusters suffer little fragmentation because almost all excess energy above the vertical ionization energy is taken away by the photoelectron, leaving only a small part of the photon energy deposited into the (HCOOH){sub n+1}{sup +} cluster. The vertical ionization energy minus the adiabatic ionization energy is enough excess energy in the clusters to surmount the proton transfer energy barrier and induce the reaction (HCOOH){sub n+1}{sup +}{yields}(HCOOH){sub n}H{sup +}+HCOO making the protonated (HCOOH){sub n}H{sup +} series dominant in all data obtained. The distribution of pure (HCOOH){sub n}H{sup +} clusters is dependent on experimental conditions. Under certain conditions, a magic number is found at n=5. Metastable dissociation rate constants of (HCOOH){sub n}H{sup +} are measured in the range (0.1-0.8)x10{sup 4} s{sup -1} for cluster sizes 4
ISSN:0021-9606
1089-7690