Browsing by Author "Luo, Pei-Ling"

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High-resolution vibration-rotational spectra and rotational perturbation of the OO-stretching ((6)) band of CH2OO between 879.5 and 932.0 cm(-1)
(2018-10-28)
Luo, Pei-Ling
;
Endo, Yasuki
;
Lee, Yuan-Pern
;
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;
應用化學系
We report the observation of a rotationally resolved (6) band associated with the OO-stretching mode of the simplest Criegee intermediate, CH2OO, in the range of 879.5-932.0 cm(-1) (11.37-10.73 m) at an optical resolution of 0.0015 cm(-1). The spectra were recorded with a tunable cw external-cavity quantum-cascade laser (EC-QCL) system coupled with a Herriott multipass absorption cell. Over one thousand lines were assigned to determine the rovibrational parameters of the (6) band. Rotational parameters A, B, and C and higher-order parameters (J), (JK), (K), (J), and (K) were determined precisely. Rotational perturbations for K-a = 3, K-a = 6, and K-a 11 on high-J levels were observed. In particular, for K-a = 6, frequency shifts as a function of J showed an avoided crossing; the shifts were analyzed in terms of a Coriolis interaction between modes (6) and (8) of CH2OO. According to the distinct temporal profiles, lines of a hot band near 899.5 cm(-1) were also identified.
Identification and Self-Reaction Kinetics of Criegee Intermediates syn-CH3CHOO and CH2OO via High-Resolution Infrared Spectra with a Quantum-Cascade Laser
(2018-08-02)
Luo, Pei-Ling
;
Endo, Yasuki
;
Lee, Yuan-Pern
;
交大名義發表
;
應用化學系
The Criegee intermediates, carbonyl oxides produced in ozonolysis of unsaturated hydrocarbons, play important roles in atmospheric chemistry. The two conformers of CH3CHOO exhibit distinct reactivity toward several atmospheric species, but a distinct conformer-specific probe is challenging because ultraviolet and infrared absorption bands of syn- and anti-CH3CHOO overlap at low-resolution. Employing a quantum-cascade laser and a Herriott cell, we recorded the O-O stretching bands of CH2OO and syn-CH3CHOO in region 880-932 cm(-1) at resolution 0.0015 cm(-1). In addition to completely resolved vibration rotational lines of CH2OO extending over 50 cm(-1), some spectral lines associated with hot bands were identified. Spectral lines solely due to syn-CH3CHOO were also identified. Probing these lines, we determined the rate coefficient for the self-reaction of syn-CH3CHOO to be k(self) = (1.6 +/-(0.5)(0.6)) x 10(-10) cm(3) molecule(-1) s(-1), about twice that of CH2OO.
Rate coefficient of the reaction CH2OO + NO2 probed with a quantum-cascade laser near 11 mu m
(2019-08-28)
Luo, Pei-Ling
;
Chung, Chen-An
;
Lee, Yuan-Pern
;
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;
應用化學系
The reaction of the simplest Criegee intermediate CH2OO with NO2 is considered to be important in atmospheric chemistry because of its prospective contribution to the decay of CH2OO and the additional source of NO3, hence its effects on the NOx and HOx cycles. The reported rate coefficients of this reaction varied by a factor of 5. Employing a cw quantum-cascade laser with wavelength near 11 mu m coupled with Herriott mirrors to probe CH2OO sensitively, we investigated in detail the reaction CH2OO + NO2 under total pressure 5.9-9.7 Torr at 298 K and reported a rate coefficient k(NO2) = (1.0 +/- 0.2) x 10(-12) cm(3) molecule(-1) s(-1), about one-seventh the value determined with direct measurements of CH2OO by Weltz et al. This smaller rate coefficient implies that the title reaction contributes to the atmospheric source of NO3 and the decay of CH2OO much less than previously conceived.