Fourier-Transform Microwave Spectroscopy of the Propargyl Radical

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Title: Fourier-Transform Microwave Spectroscopy of the Propargyl Radical
Creators: Tanaka, Takehiko; Ohshima, Yasuhiro; Endo, Yasuki
Issue Date: 1994
Publisher: Ohio State University
Abstract: The $1_{0.1} \leftarrow O_{0.0}$ rotational spectrum of the propargyl radical $(CH_{2}C-CH)$ was observed by a Fourier-transform microwave spectrometer with pulsed discharge nozzale. The propargyl radical was produced by dc discharge $(\sim 1.3$ kV. 200mA) of propargyl chloride $(ClCH_{2}C-CH)$ diluted to 0.25% with 5 atom Ar (0.25%) and injected into an absorption cell through the pulsed nozzle with the repetition rate of 5 Hz. The rotational temperature of the propargyl was estimated as low as a few K. The rotational transition. $1_{0.1} \leftarrow O_{0.0}$. Observed was splitted into twelve components due to the electron spin-rotation interaction ($J=0.5 \leftarrow 0.5$ and $1.5 \leftarrow 0.5$) and the hyperfine interaction because of the three H nuclei (I = 0.5). The rotational, centrifugal distortion, and spin-rotation constants for the ground state, $A=288045.5(34), \widetilde{B}= 9365.2766(73). B-C = 316.30(23), \varepsilon_{aa}-544.2(29), \varepsilon_{bb} =-11.043(037)$, and $\varepsilon_{cc}= -1.0$(fixed) MHz, as well as the hyperfine interaction constants, of $\alpha F, T_{00}$ and $T_{bb}$, for both the acetylenic (I=0.5) and methylenic (I=1) protons were derived from the MW spectrum combined with the infrared diode laser spectra of the $v_{6}$ fundamental band (1).The dipole moment of the propargyl radical is estimated to be less than 0.2 D from the microwave power dependence of the spectrum, which ageress with the recent ab initio calculation, 0.14 D (2). The figures in parentheses are standard deviation to be attached to the last digit.
Description: (1) K. Tanaka, T. Harada, K. Sakaguchi, and T. Tanaka, to be published. (2) P. Botschwina. Private communication.
Author Institution: Department of Chemistry, Faculty, of Science, Kyushu University 33, Hakozaki; Department of pure and applied Science, College of Arts and Science, The University of Tokyo
Other Identifiers: 1994-MG-10
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