Core-to-Rydberg band shift and broadening of hydrogen bonded ammonia clusters studied with nitrogen K-edge excitation spectroscopy
- Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526 (Japan)
Nitrogen 1s (N ls) core-to-Rydberg excitation spectra of hydrogen-bonded clusters of ammonia (AM) have been studied in the small cluster regime of beam conditions with time-of-flight (TOF) fragment-mass spectroscopy. By monitoring partial-ion-yield spectra of cluster-origin products, ''cluster'' specific excitation spectra could be recorded. Comparison of the ''cluster'' band with ''monomer'' band revealed that the first resonance bands of clusters corresponding to N 1s{yields} 3sa{sub 1}/3pe of AM monomer are considerably broadened. The changes of the experimental core-to-Rydberg transitions {Delta}FWHM (N 1s{yields} 3sa{sub 1}/3pe) ={approx}0.20/{approx}0.50 eV compare well with the x ray absorption spectra of the clusters generated by using density functional theory (DFT) calculation. The broadening of the core-to-Rydberg bands in small clusters is interpreted as being primarily due to the splitting of non-equivalent core-hole N 1s states caused by both electrostatic core-hole and hydrogen-bonding (H{sub 3}N{center_dot}{center_dot}{center_dot}H-NH{sub 2}) interactions upon dimerization. Under Cs dimer configuration, core-electron binding energy of H-N (H-donor) is significantly decreased by the intermolecular core-hole interaction and causes notable redshifts of core-excitation energies, whereas that of lone-pair nitrogen (H-acceptor) is slightly increased and results in appreciable blueshifts in the core-excitation bands. The result of the hydrogen-bonding interaction strongly appears in the n-{sigma}* orbital correlation, destabilizing H-N donor Rydberg states in the direction opposite to the core-hole interaction, when excited N atom with H-N donor configuration strongly possesses the Rydberg component of anti-bonding {sigma}* (N-H) character. Contributions of other cyclic H-bonded clusters (AM){sub n} with n{>=} 3 to the spectral changes of the N 1s{yields} 3sa{sub 1}/3pe bands are also examined.
- OSTI ID:
- 22047153
- Journal Information:
- Journal of Chemical Physics, Vol. 136, Issue 1; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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