Photoionization of As sub 2 and As sub 4 : Implications for group V clusters

Journal Article · Fri May 01 00:00:00 EDT 1992 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.462579· OSTI ID:7034804

Yoo, R K; Ruscic, B; Berkowitz, J ^[1]

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1. Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

The vacuum ultraviolet photoionization mass spectrum of As{sub 4} is presented, from the ionization threshold to 600 A. The apparent adiabatic ionization potential is {le}8.49 eV, but the true value may be significantly lower. Three broad autoionization features are observed, probably comprising members of a Rydberg series converging to the {ital {tilde B}} {sup 2}{ital A}{sub 1} state of As{sup +}{sub 4}. The first fragment, As{sup +}{sub 3}, has an appearance potential (0 K) of 11.23{plus minus}0.05 eV, from which we extract {Delta}{ital H}{sup 0}{sub {ital f}{sub 0}}(As{sup +}{sub 3}){le}228.7{plus minus}1.3 kcal/mol. The photoion yield curve of As{sup +}{sub 2}(As{sub 2}) is obtained under conditions where As{sub 2} is dominant in the vapor. The adiabatic ionization potential is 9.69{plus minus}0.02 eV. Two prominent autoionizing Rydberg series are observed, converging to the {ital A} {sup 2}{Sigma}{sup +}{sub {ital g}} state of As{sup +}{sub 2}, with an ionization potential of 10.238{plus minus}0.002 eV. At higher energy, three members of a window resonance series can be seen, converging to the {ital B} {sup 2}{Sigma}{sup +}{sub {ital u}} state of As{sup +}{sub 2}, with an ionization potential of 15.37 eV. From an upper limit to the partial pressure of As{sub 3}, equilibrium conditions, and assuming a triangular As{sub 3}, we deduce {Delta}{ital H}{sup 0}{sub {ital f}{sub 0}}(As{sub 3}){ge}60.0 kcal/mol; other criteria suggest {Delta}{ital H}{sup 0}{sub {ital f}{sub 0}}(As{sub 3}){congruent}63 kcal/mol. Consequently, the adiabatic ionization potential of As{sub 3} is {lt}7.32 eV, and probably {le}7.19 eV. Several implications are drawn, relevant to recent studies of antimony and bismuth clusters.

• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 7034804
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 96:9; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

664500* -- Special Atoms & Molecules-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ADIABATIC PROCESSES
ANTIMONY
ARSENIC
AUTOIONIZATION
BISMUTH
CHARGED PARTICLES
ELECTROMAGNETIC RADIATION
ELEMENTS
ENERGY
EXPANSION
FAR ULTRAVIOLET RADIATION
FLUID FLOW
IONIZATION
IONIZATION POTENTIAL
IONS
MASS SPECTRA
METALS
PHOTOIONIZATION
RADIATIONS
SEMIMETALS
SPECTRA
SUPERSONIC FLOW
THRESHOLD ENERGY
ULTRAVIOLET RADIATION
YIELDS