Two-color zero kinetic energy photoelectron spectra of benzonitrile and its vanderWaals complexes with argon. Adiabatic ionization potentials and cation vibrational frequencies
Two-color zero kinetic energy photoelectron spectra of benzonitrile and its vanderWaals complexes with argon. Adiabatic ionization potentials and cation vibrational frequencies
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DOI：
10.1021/jp960565a
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发表时间：
1996-06-20
影响因子：
--
通讯作者：
Kimura, K
中科院分区：
文献类型：
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作者：
Araki, M;Sato, S;Kimura, K
利用双色零动能光电子能谱（ZEKE）首次研究了超声速射流中苯腈及其与氩（苯腈- ar和苯腈- ar -2）的范德华配合物。从第一电子激发态（S-1）得到的（1+1’）ZEKE光电子能谱中，我们确定了I-a（苯并腈）= 78 490 +/- 2 cm(-1) （9.7315 +/- 0.0002 eV）、I-a（苯并腈- ar） = 78 241 +/- 4 cm(-1) （9.7007 +/- 0.0005 eV）和I-a（苯并腈- ar -2） = 78 007 +/- 4 cm(-1) （9.6716 +/- 0.0005 eV）的绝热电离势。这些值表明，与其他单取代苯相比，由于络合物的形成（δ I-a分别= -249和-483 cm(-1)），电离电位的下降非常大。在ZEKE光电子能谱中，发现了1300 cm（-1）以下的裸苯腈阳离子的11种低频振动模式。从S-1振动能级33(1)和22(2)得到的ZEKE光电子能谱中，可以清楚地识别出面内C-C=N弯曲模式（33(+)）和面外C-C- c弯曲模式（22(+)）。此外，在苯腈- ar和-Ar-2光谱中，我们观察到分别为12和9 cm（-1）的极低频率的振动进展，这些振动进展可能分别属于vdW弯曲模式(b（x)(+)）和vdW对称弯曲模式(b（xx)(+)）。
Benzonitrile and its van der Waals (vdW) complexes with argon (benzonitrile-Ar and benzonitrile-Ar-2) have been studied in supersonic jets by two-color zero-kinetic-energy (ZEKE) photoelectron spectroscopy for the first time. From the (1+1') ZEKE photoelectron spectra obtained via the first electronic excited state (S-1), we have determined adiabatic ionization potentials as I-a(benzonitrile) = 78 490 +/- 2 cm(-1) (9.7315 +/- 0.0002 eV), I-a(benzonitrile-Ar) = 78 241 +/- 4 cm(-1) (9.7007 +/- 0.0005 eV), and I-a(benzonitrile-Ar-2) = 78 007 +/- 4 cm(-1) (9.6716 +/- 0.0005 eV). These values indicate that the decrease in ionization potential due to the complex formation (Delta I-a = -249 and -483 cm(-1), respectively) is very large compared with other monosubstituted benzenes. Eleven low-frequency vibrational modes of the bare benzonitrile cation below 1300 cm(-1) have been identified in the ZEKE photoelectron spectra. The in-plane C-C=N bending mode (33(+)) and the out-of-plane C-C-C bending mode (22(+)) have been clearly identified from the ZEKE photoelectron spectra obtained via the S-1 vibrational levels 33(1) and 22(2), respectively. Furthermore, in the benzonitrile-Ar and -Ar-2 spectra, we have observed well-resolved vibrational progressions with very low frequencies of 12 and 9 cm(-1), respectively, which may be assigned to the vdW bending mode (b(x)(+)) and the vdW symmetric bending mode (b(xx)(+)) along the substituent axis, respectively.