Halide fluorescence spectroscopy

Conventional molecular beam reactive scattering studies have excelled in the determination of the angular and velocity distributions of reaction products, but direct information on the internal state distributions has been sparse. One of the most important of the non-beam methods for learning about the partitioning of reaction energy into the internal degrees of freedom of the products has been infra-red chemiluminescence studies. Unfortunately, this technique has hitherto been limited to hydride compounds, principally hydrogen halides. We present an alternative technique based on electronic fluorescence spectroscopy. 

The second method (ASTM D-4294, IP 477) uses energy-dispersive X-ray fluorescence spectroscopy, has slightly better repeatability and reproducibility than the high-temperature method, and is adaptable to field applications but can be affected by some commonly present interferences such as halides. In this method, the sample is placed in a beam emitted from an X-ray source. The resultant excited characteristic X radiation is measured, and the accumulated count is compared with counts from previously prepared calibration standard to obtain the sulfur concentration. Two groups of calibration standards are required to span the concentration range, one standard ranges from 0.015% to 0.1% w/w sulfur and the other from 0.1% to 5.0% w/w sulfur. 

Other classes of alkaloids, which exhibit fluorescence, include the quinoline and isoquinoline alkaloids. Quinoline is weakly fluorescent. The anti-malarial drug quinine includes a methoxy substituent on the 6 position of the quinoline moiety and fluoresces very intensely. Quinine, in sulfuric acid solution, is often used as a standard in fluorescence spectroscopy for determining a quantum yield. Its fluorescent properties are sensitive to pH. At pH 2 it has an excitation maximum of 347 nm with fluorescence at 448 nm. At pH 7 the peaks shift to absorb at 331 nm and emit at 382 nm. In hydrochloric acid solution, absorption is unaffected but fluorescence intensity is quenched greatly by the halide anions. 

K.Shimoda Introduction. - KShimoda Line Broadening and Narrowing Effects. - PJacquinot Atomic Beam Spectroscopy. - K 5. Letokhov Saturation Spectroscopy. -J.L Hall, J. A Magyar High Resolution Saturated Absorption Studies of Methane and Some Methyl-Halides. -V. D. 0 6 /)ort v. Three-Level Laser Spectroscopy. -S. Haroche C antum Beats and Time-Resolved Fluorescence Spectroscopy. N. Bloembergen,... 

The photolysis of aniline at high temperatures results in N-H and C-N clea-vage, but at room temperature the major reaction is fluorescence. Below 2800 A some photodecomposition takes place the lifetime and dissociation probability of excited aniline molecules have been calculated Flash photolysis of aniline followed by kinetic mass spectroscopy failed to reveal the presence of dissociation products. Irradiation of halogen derivatives of aniline between 2480 and 2562 A produces halide ions in measurable yields . Positive mesomeric effects increase, and negative mesomeric effects decrease... 

The diatomic yttrium halides have been the topic of both ab initio and experimental studies. Fischell et al. (1980) have studied the excitation spectra of the YCl diatomic molecule using the laser-induced fluorescence (LIF) method. More recently, Xin et al. (1991) have studied the B ri-X system of YCl in high resolution. The rotational analysis of the observed bands has yielded very accurate molecular constants for the X and B states of YCl. Shirley et al. (1990) have studied the molecular-beam optical Stark spectrum of the B n(t = 0)-X (t = 0) band system of YF. The permanent dipole moment and the magnetic hyperfine parameter a for the B n state have been determined as 2.96(4) D and 146.8(3) MHz, respectively. The dipole moment of the X S state was determined as 1.82(8)D. More recently, Shirley et al. (1991) have employed the molecular-beam millimeter-wave optical pump-probe spectroscopy to study pure rotational transitions of the YF ground state. This study has yielded improved ground-state rotational constants as B = 8683.65(1) MHz and D = 0.0079(2)-MHz, respectively. 

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