TY - JOUR
T1 - Photoelectron spectroscopy of cluster anions of naphthalene and related aromatic hydrocarbons
AU - Ando, Naoto
AU - Mitsui, Masaaki
AU - Nakajima, Atsushi
N1 - Funding Information:
This work was partially supported by Grant-in-Aids on Priority Area “Molecular Theory for Real Systems” (No. 19029041) and for Young Scientist (B), (No. 14740332 and No. 17750016) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (MEXT). N.A. is grateful to JSPS Research Fellowships for Young Scientists.
PY - 2008
Y1 - 2008
N2 - The electronic structures and structural morphologies of naphthalene cluster anions, (naphthalene) n- (n=3-150), and its related aromatic cluster anions, (acenaphthene) n- (n=4-100) and (azulene) n- (n=1-100), are studied using anion photoelectron spectroscopy. For (naphthalene) n- clusters, two isomers coexist over a wide size range: isomers I and II-1 (28≤n≤60) or isomers I and II-2 (n∼60). Their contributions to the photoelectron spectra can be separated using an anion beam hole-burning technique. In contrast, such an isomer coexistence is not observed for (acenaphthene) n- and (azulene) n- clusters, where isomer I is exclusively formed throughout the whole size range. The vertical detachment energies (VDEs) of isomer I (7≤n≤100) in all the anionic clusters depend linearly on n-13 and their size-dependent energetics are quite similar to one another. On the other hand, the VDEs of isomers II-1 and II-2 produced in (naphthalene) n- clusters with n∼30 remain constant at 0.84 and 0.99 eV, respectively, 0.4-0.6 eV lower than those of isomer I. Based upon the ion source condition dependence and the hole-burning photoelectron spectra experiments for each isomer, the energetics and characteristics of isomers I, II-1, and II-2 are discussed: isomer I is an internalized anion state accompanied by a large change in its cluster geometry after electron attachment, while isomers II-1 and II-2 are crystal-like states with little structural relaxation. The nonappearance of isomers II-1 and II-2 for (acenaphthene) n- and (azulene) n- and a comparison with other aromatic cluster anions indicate that a highly anisotropic and symmetric π -conjugated molecular framework, such as found in the linear oligoacenes, is an essential factor for the formation of the crystal-like ordered forms (isomers II-1 and II-2). On the other hand, lowering the molecular symmetry makes their production unfavorable.
AB - The electronic structures and structural morphologies of naphthalene cluster anions, (naphthalene) n- (n=3-150), and its related aromatic cluster anions, (acenaphthene) n- (n=4-100) and (azulene) n- (n=1-100), are studied using anion photoelectron spectroscopy. For (naphthalene) n- clusters, two isomers coexist over a wide size range: isomers I and II-1 (28≤n≤60) or isomers I and II-2 (n∼60). Their contributions to the photoelectron spectra can be separated using an anion beam hole-burning technique. In contrast, such an isomer coexistence is not observed for (acenaphthene) n- and (azulene) n- clusters, where isomer I is exclusively formed throughout the whole size range. The vertical detachment energies (VDEs) of isomer I (7≤n≤100) in all the anionic clusters depend linearly on n-13 and their size-dependent energetics are quite similar to one another. On the other hand, the VDEs of isomers II-1 and II-2 produced in (naphthalene) n- clusters with n∼30 remain constant at 0.84 and 0.99 eV, respectively, 0.4-0.6 eV lower than those of isomer I. Based upon the ion source condition dependence and the hole-burning photoelectron spectra experiments for each isomer, the energetics and characteristics of isomers I, II-1, and II-2 are discussed: isomer I is an internalized anion state accompanied by a large change in its cluster geometry after electron attachment, while isomers II-1 and II-2 are crystal-like states with little structural relaxation. The nonappearance of isomers II-1 and II-2 for (acenaphthene) n- and (azulene) n- and a comparison with other aromatic cluster anions indicate that a highly anisotropic and symmetric π -conjugated molecular framework, such as found in the linear oligoacenes, is an essential factor for the formation of the crystal-like ordered forms (isomers II-1 and II-2). On the other hand, lowering the molecular symmetry makes their production unfavorable.
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U2 - 10.1063/1.2903473
DO - 10.1063/1.2903473
M3 - Article
C2 - 18433220
AN - SCOPUS:42449132298
VL - 128
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
SN - 0021-9606
IS - 15
M1 - 154318
ER -