Jet-cooled laser-induced fluorescence spectroscopy of methylcyclohexoxy radicals

Lin, Jinxin; Wu, Qixin; Liang, Gaiting; Zu, Lily; Fang, Wei‐Hai

doi:10.1039/c1ra00216c

Cited by 10 publications

(70 citation statements)

References 20 publications

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“…11 The vibronic bands are labeled by capitalized letters following ref 11. In this section, we first present the results of 4-MCHO, which has nominal C s symmetry, followed by the 3-and 2-MCHO radicals.…”

Section: Resultsmentioning

confidence: 99%

“…11 Both observations may be explained by the interaction between the oxygen atom and the methyl group: Of the three isomers, the methyl group is closest to the oxygen atom in 2-MCHO and hence the strongest interaction.…”

Section: Symmetry Of A/x̃states and Transitionmentioning

confidence: 95%

“…11 Such analysis allowed the assignment of vibronic bands in the LIF spectra and suggests that all LIF bands observed under jetcooled conditions are due to the lowest-energy conformers of each isomer. The six-membered ring in these conformers has chair structure, and both the oxygen atom and the methyl group are at the equatorial positions.…”

Section: Quantum Chemical Calculationsmentioning

confidence: 99%

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Dispersed Fluorescence Spectroscopy of Jet-Cooled 2-, 3-, and 4-Methylcyclohexoxy Radicals

et al. 2015

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Vibrational structures of the nearly degenerate X̃ and Ã states of the 2-, 3-, and 4-methylcyclohexoxy (MCHO) radicals were studied by jet-cooled dispersed fluorescence (DF) spectroscopy. The observed transitions were assigned on the basis of vibrational frequencies and Franck-Condon factors predicted by quantum chemical calculations. Intensities of vibronic transitions in the DF spectra are dependent on the laser-induced fluorescence (LIF) bands pumped in the experiment, which can be explained by the difference in geometry and symmetry between the lower X̃/Ã states and the highly excited B̃ state. All three studied isomers of MCHO have close-lying X̃ and Ã states although their energy separations are affected by the position of the methyl group. It is suggested by quantum chemical calculations that the lowest-energy conformers of all three isomers have the half-filled orbital oriented perpendicular to the OCH plane, which is consistent with the observed relative intensities of the B̃ → X̃ and B̃ → Ã origin bands. When the origin and the CO-stretch bands of the B̃ ← X̃ LIF excitation spectra were pumped, the DF spectra were dominated by CO-stretch progressions. When non-CO-stretch vibrational levels of the B̃ state were pumped, progressions of CO-stretch modes combined with the pumped vibrational mode were observed. Excited-state vibrational population relaxation from the CO stretch level to the vibrational ground level and from combination levels of the CO stretch mode and other vibrational modes to the non-CO stretch modes was observed. Analysis of the DF spectra confirms the previous conclusion that all strong LIF bands observed under jet-cooled conditions belong to a single conformer of each positional isomer (Lin et al. RSC Adv. 2012, 2, 583-589).

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Section: Resultsmentioning

confidence: 99%

Section: Symmetry Of A/x̃states and Transitionmentioning

confidence: 95%

Section: Quantum Chemical Calculationsmentioning

confidence: 99%

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Dispersed Fluorescence Spectroscopy of Jet-Cooled 2-, 3-, and 4-Methylcyclohexoxy Radicals

et al. 2015

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“…Previously, the B̃ ← X̃ transitions of all four isomers of MCHO were studied in laser-induced fluorescence (LIF) spectroscopy under jet-cooled conditions. 36,37 Both the origin band frequencies and vibronic structures of these isomers are different from each other. Such observation confirms the effect of methyl substitution on the B̃ state vibrational structure.…”

Section: Discussionmentioning

confidence: 93%

“…Furthermore, they did not assign their reported LIF spectrum of isopentoxy radicals. Also, Lin et al 36 and Wu et al 37 reported the first observation of jet-cooled LIF excitation spectra of all four MCHO isomer. Their spectra stimulated us to try to obtain simpler, jet-cooled LIF and DF spectra of these species.…”

Section: Alkoxy Radicalsmentioning

confidence: 98%

Laster spectroscopic investigations of organic alkoxy and peroxy radicals.

Reza¹

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like to thank the department for having faith in me and admitting me into the Ph.D. program. First, I would like to express my gratitude to my advisor, Jinjun Liu, for his constant guidance and support and for giving me training in science beyond my imagination. His time and patience were really helpful in achieving my goals. I need to also acknowledge my dissertation defense committee members, Dr. Richard J. Wittebort, Dr. Lee Thompson, and Dr. Sergio B. Mendes. Thanks for being there in the key moment of my graduate school career. Next, I have to thank Neil J. Reilly to whom I owe a lot of what I know about the laser-induced fluorescence and dispersed fluorescence system. It was a wonderful experience to work with all the other members of the Liu group, specially Opu, and Hamzeh. I also want to acknowledge the incredible support from the staff, especially Steve, Sherry, Carla, Ben, Jason, and Renu, in the Department of Chemistry. Your kindness and care towards me have been very welcoming during my time here at UofL. v I thank my parents, who always encouraged me and took great pride in my progress in this endeavor. Outside of my lab, I am very much indebted to my dearest friend Dhruba Kumar Pattadar for his timely help and invaluable suggestions during my Ph.D. course work. I am also grateful to my brother and their families for their support and advice in every possible way. My in-laws have stood by me always. I thank them for their encouragement. Finally, I would like to thank my beloved wife, Rumpa, for being with me and her encouragement and support to pursue my Ph.D. degree.

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CH₃O Substitution Effect Revisited in the Vibrationally Resolved Laser-Induced Fluorescence Spectra of Methoxycyclohexoxy Radicals

Zou,

Yu,

Liu

et al. 2024

J. Phys. Chem. A

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The oxy-substituted alkoxy radicals have attracted wide attention due to the increasing application of oxygenated volatile organic compounds as fuel additives and solvents. Direct detection of these intermediate radicals is desired for measuring the reaction rate and investigating the oxidation mechanism of organic compounds in the atmosphere. A charge-transfer excited state induced by CH 3 O substitution was identified in our previous study of 3-methoxy-1-propoxy radical [Xue, J. et al. Phys. Chem. Chem. Phys. 2021, 23, 2586. As the C−C bonds of chain alkoxy radicals can freely rotate, further studies are needed to understand the mechanism of this long-range charge-transfer effect. In this work, vibrational-resolved laser-induced fluorescence (LIF) spectra of 3and 4-methoxycyclohexoxy radicals were obtained under jet-cooled conditions. A large red-shift of ∼454 cm −1 of the origin band was observed when the CH 3 O substituent moved from the δ site to the γ site of the cyclohexoxy radical. The LIF spectra are assigned to 3-cis (e, e) and 4-trans (e, e) conformers, respectively, with the assistance of structural optimization and electron excitation studies conducted at the CAM-B3LYP/6-311++G(d,p) level of theory. Natural transition orbital analysis reveals that the intramolecular charge transfer from the C−O−C p orbital to the radical O p orbital in 3-methoxycyclohexoxy has a strong effect on the radical CO σ → O p excitation and hence results in a spectral change. On the other hand, the spectral effect of CH 3 O substitution almost vanishes at δ carbon. The results propose a through-bond interaction between CH 3 O and radical CO groups.

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Jet-cooled laser-induced fluorescence spectroscopy of methylcyclohexoxy radicals

Cited by 10 publications

References 20 publications

Dispersed Fluorescence Spectroscopy of Jet-Cooled 2-, 3-, and 4-Methylcyclohexoxy Radicals

Dispersed Fluorescence Spectroscopy of Jet-Cooled 2-, 3-, and 4-Methylcyclohexoxy Radicals

Laster spectroscopic investigations of organic alkoxy and peroxy radicals.

CH₃O Substitution Effect Revisited in the Vibrationally Resolved Laser-Induced Fluorescence Spectra of Methoxycyclohexoxy Radicals

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Jet-cooled laser-induced fluorescence spectroscopy of methylcyclohexoxy radicals

Cited by 10 publications

References 20 publications

Dispersed Fluorescence Spectroscopy of Jet-Cooled 2-, 3-, and 4-Methylcyclohexoxy Radicals

Dispersed Fluorescence Spectroscopy of Jet-Cooled 2-, 3-, and 4-Methylcyclohexoxy Radicals

Laster spectroscopic investigations of organic alkoxy and peroxy radicals.

CH3O Substitution Effect Revisited in the Vibrationally Resolved Laser-Induced Fluorescence Spectra of Methoxycyclohexoxy Radicals

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CH₃O Substitution Effect Revisited in the Vibrationally Resolved Laser-Induced Fluorescence Spectra of Methoxycyclohexoxy Radicals