實驗簡介和儀器設備

從研究多取代基苯衍生物中我們發現以下有趣的現象，統稱為取代基對絕熱游離能的效應(1."MOP"定則 2.重元素效應 3.長碳鏈效應)：

1. "MOP" 定則：絕熱游離能的大小順序是"間 > 鄰 > 對 (即 meta > ortho > para)"

ionization energy:
m-fluoroaniline (64159 cm^-1) > o-fluoroaniline (63644 cm^-1) > p-fluoroaniline (62543 cm^-1)

“Ionization energy of p-fluoroaniline and vibrational levels of p-fluoroaniline cation determined by mass-analyzed threshold ionization spectroscopy”, W. B. Tzeng and J. L. Lin, J. Phys. Chem. A 103, 8612–8619 (1999).
“Ionization energy of o-fluoroaniline and vibrational levels of o-fluoroaniline cation determined by mass-analyzed threshold ionization spectroscopy, J. L. Lin and W. B. Tzeng, Phys. Chem. Chem. Phys. 2, 3759–3763 (2000).
“Species-selected mass analyzed threshold ionization spectra of m-fluoroaniline cation”, J. L. Lin, K. C. Lin, and W. B. Tzeng, Appl. Spectrosc. 55, 120–124 (2001).

其他的雙取代基苯衍生物:

o-, m-, p-dimethoxybenzene

o-, m-, p-fluoroanisole

o-, m-, p-fluorophenylacetylene

o-, m-, p-methoxyaniline

o-, m-, p-methylaniline

Measured adiabatic ionization energies (in cm^-1) of di-substituted benzenes and MOP propensity
(The uncertainty of these listed values is about 5 cm^-1)

Ionization energy	meta	ortho	para	ref.
Methoxyaniline (OCH₃) (NH₂)	59983 (cis) ^a 60879 (trans) ^a	58678 (trans) ^a	57445 ^b	^a J. Mol. Spectrosc. 244 (2007) 1 ^b Chem. Phys. Lett. 370 (2003) 44
Methylaniline (CH₃) (NH₂)	61059^a	61002^a	60160^a	^a J. Phys. Chem. A 106 (2002) 6462
Dimethoxybenzene (OCH₃)*2	63523 (a)^a 64491 (b)^a 63758 (c)^a	61617^a	60772 (cis) ^b 60563 (trans) ^b	^a J. Phys. Chem. A 114 (2010) 11144 ^b J. Phys. Chem. A 105 (2001) 11455
Methoxyphenol (OCH₃) (OH)	65288(I)^a 65648(III)^a 64741(IV)^a	63990 (trans) ^b	62313 (cis) ^c 62210 (trans) ^c	^a J. Phys. Chem. A 104 (2000) 11864 ^b Chem. Phys. 323 (2006) 429 ^c Chem. Phys. Lett. 410 (2005) 99
Fluoroaniline (F) (NH₂)	64159^a	63644 ^b	62543 ^c	^a Appl. Spectrosc. 55 (2001) 120 ^b Phys. Chem. Chem. Phys. 2 (2000) 3759 ^c J. Phys. Chem. A 103 (1999) 8612
Dihydroxybenzene (OH)*2	66695 (cis)^a 67148 (trans)^a	65878^a	64054 (cis)^a 63999 (trans)^a	^a J. Chem. Phys. 111 (1999) 7966
Hydroxytoluene (OH) (CH₃)	66933 (cis)^a 67084 (trans)^a	66855 (cis) ^b 66785 (trans) ^b	65918 ^c	^a Spectrochim. Acta A Mol. Biomol. Spectrosc. 67 (2007) 989 ^b J. Electron. Spectros. Relat. Phenomena 108 (2000) 13 ^c J. Chem. Phys. 120 (2004) 10513
Aminobenzonitrile (CN) (NH₂)	66852^a	66653 ^b	66493 ^c	^a Our lab ^b Chem. Phys. Lett. 692 (2018) 395 ^c Chem. Phys. 261 (2000) 449
Fluoroanisole (F) (OCH₃)	67867 (cis)^a 68304 (trans)^a	67354^b	66437 ^b	^a J. Mol. Spectrosc. 274 (2012) 43 ^b Chem. Phys. Lett. 524 (2012) 38
Fluorostyrene (F) (C=CH₂)	69960 (cis)^a 69856 (trans)^a	69304 (trans)^b	68244 ^c	^a J. Mol. Spectrosc. 316 (2015) 72 ^b J. Mol. Spectrosc. 332 (2017) 3 ^c J. Chem. Phys. 120 (2004) 8015
Fluorophenol (F) (OH)	70164 (cis)^a 70425 (trans)^a	70006 (cis)^b	68577 ^c	^a Phys. Chem. Chem. Phys. 4 (2002) 2534 ^b Chem. Phys. 323 (2006) 429 ^c Chem. Phys. Lett. 390 (2004) 65
Fluorotoluene (F) (CH₃)	71997^a	71858 ^b	70946 ^c	^a J. Chem. Phys. 151 (2019) 084311 ^b J. Chem. Phys. 99 (1993) 3205 ^c J. Chem. Phys. 145 (2016) 124307
Fluorophenylacetylene (F) (C≡CH)	72598^a	71976^a	70999^a	^a J. Phys. Chem. A 118 (2014) 8277
Dichlorobenzene (Cl)*2	73776^a	73237^a	72191^a	^a J. Phys. Chem. A 112 (2008) 425
Difluorobenzene (F)*2	75339^a	74979^a	73872 ^b	^a J. Phys. Chem. 96 (1992) 99 ^b J. Phys. Chem. 97 (1993) 4335
Cyanotoluene (C≡N) (CH₃)	75850^a	75732^a	75155	^a J. Electron Spectros. Relat. Phenomena 142 (2005) 215

2. "重元素效應" ：鹵化物的絕熱游離能的大小順序是氟 > 氯 > 溴 (越重的鹵化物，它的絕熱游離能越小)

ionization energy:

p-fluoroaniline (62543 cm^-1) > p-chloroaniline (62410 cm^-1) > p-bromoaniline (62308 cm^-1)

“Ionization energy of p-fluoroaniline and vibrational levels of p-fluoroaniline cation determined by mass-analyzed threshold ionization spectroscopy”, W. B. Tzeng and J. L. Lin, J. Phys. Chem. A 103, 8612–8619 (1999).

“Mass analyzed threshold ionization of the ³⁵Cl and ³⁷Cl isotopomers of p-chloroaniline”, J. L. Lin and W. B. Tzeng, J. Chem. Phys. 113, 4109–4115 (2000).

“Mass analyzed threshold ionization of p-bromoaniline: Heavy atom effects on electronic transition, ionization, and molecular vibration”, J. L. Lin, S. C. Yang, Y. C. Yu, and W. B. Tzeng, Chem. Phys. Lett. 356, 267–276 (2002).

3. "長碳鏈效應" ：烷基化合物的絕熱游離能的大小順序是甲烷 > 乙烷 > 丙烷 (碳鏈越長的烷基鹵化物，它的絕熱游離能越小)

ionization energy:

p-methylaniline (60160 cm^-1) > p-ethylaniline (59959 cm^-1)

“Mass analyzed threshold ionization spectroscopy of o-, m-, p-methylaniline cations: Vicinal substitution effects on electronic transition, ionization, and molecular vibration”, J. L. Lin, K. C. Lin, and W. B. Tzeng, J. Phys. Chem. A 106, 6462–6468 (2002).

“Mass analyzed threshold ionization spectroscopy of p-ethylaniline cation: Alkyl chain effects on ionization and molecular vibration”, S. C. Yang, J. L. Lin, and W. B. Tzeng, Chem. Phys. Lett. 362, 19–25 (2002).

p-methylphenol (65918 cm^-1) > p-ethylphenol (65628 cm^-1) > p-n-propylphenol, gauche-A (65385 cm^-1) > p-n-propylphenol, gauche-B (65369 cm^-1) > p-n-propylphenol, trans (65283 cm^-1)

“Mass-analyzed threshold ionization spectroscopy of p-methylphenol and p-ethylphenol cations and the alkyl substitution effect”, Jung Lee Lin, Changyong Li, and Wen Bih Tzeng, J. Chem. Phys. 120, 10513–10519 (2004).

“Mass-analyzed threshold ionization spectroscopy of the rotamers of p-n-propylphenol cation and configuration effect”, Changyong Li, Jung Lee Lin, and Wen Bih Tzeng, J. Chem. Phys. 122, 044311 (2005). [10 pages]

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