Molecular-beam resonance spectroscopy

The resulting spectrum represents a weighted average over the rotational states and a careful analysis of it yields the nuclear quadrupole coupling constant. Molecular beam electric resonance is complementary to pure rotational spectroscopy since transitions between the Stark levels of the rotational states (AJ = 0) are observed (sometimes AJ= 1 transitions are also studied). Specially constructed maser spectrometers55 that can detect transitions of rotationally selected molecules have been used to determine very small coupling constants, such as those for deuterium compounds. Again, molecular beam resonance is currently limited to the study of small molecules. 

Meth. MW MB IR MODR method of measurement used in the given reference corresponding to the preceding quoted values microwave spectroscopy molecular beam resonance experiment-electric or magnetic resonance infrared with lasers microwave optical double resonance... 

Meth. LC QB OS ED MW MB EPR DR method of measurement for the values in this line of the table level crossing spectroscopy quantum beat spectroscopy optical spectroscopy electric deflection method microwave spectroscopy molecular beam resonance experiment-electric or magnetic resonance electron paramagnetic resonance double resonance experiments (MODR, RF/DR)... 

Meth. DR LA LM MB MW RA method of measurement applied to obtain the reported value double resonance experiments (microwave-optical double resonance MODR or radiofrequency-optical double resonance RFDR) Doppler free laser spectrosefipy laser magnetic resonance molecular beam electric resonance or molecular beam resonance with laser detection method microwave spectroscopy radio astronomy... 

In dimers composed of equal molecules the dimer components can replace each other through tunneling. This effect has been discovered by Dyke et al. [1972] as interconversion splitting of rotational levels of (HF)2 in molecular beam electric resonance spectra. This dimer has been studied in many papers by microwave and far infrared tunable difference-frequency laser spectroscopy (see review papers by Truhlar [1990] and by Quack and Suhm [1991]). The dimer consists of two inequivalent HE molecules, the H atom of one of them participating in the hydrogen bond between the fluorine atoms (fig. 60). PES is a function of six variables indicated in this figure. 

Dyke, T.R., Mack, K.M. and Muenter, J.S. (1977) The structure of water dimer from molecular beam electric resonance spectroscopy, J. Chem. Phys., 66,498-510. 

Other measurements. Induced dipole moments can be measured by most of the familiar methods that are designed to measure permanent dipole moments. We mention in particular the beam deflection method by electric fields, using van der Waals molecules, and molecular beam electric resonance spectroscopy of van der Waals molecules [373, 193, 98]. 

Although theoretical techniques for the characterization of resonance states advanced, the experimental search for reactive resonances has proven to be a much more difficult task [32-34], The extremely short lifetime of reactive resonances makes the direct observation of these species very challenging. In some reactions, transition state spectroscopy can be employed to study resonances through "half-collision experiments," where even very short-lived resonances may be detected as peaks in a Franck-Condon spectrum [35-38]. Neumark and coworkers [39] were able to assign peaks in the [IHI] photodetachment spectrum to resonance states for the neutral I+HI reaction. Unfortunately, transition state spectroscopy is not always feasible due to the absence of an appropriate Franck-Condon transition or due to practical limitations in the required level of energetic resolution. The direct study of reactive resonances in a full collision experiment, such as with a molecular beam apparatus, is the traditional and more usual environment to work. Unfortunately, observing resonance behavior in such experiments has proven to be exceedingly difficult. The heart of the problem is not a... 

The present work involves measurement of k in a 0.1 atmosphere, stoichiometric CH -Air flame. All experiments were conducted using 3 inch diameter water-cooled sintered copper burners. Data obtained in our study include (a) temperature profiles obtained by coated miniature thermocouples calibrated by sodium line reversal, (b) NO and composition profiles obtained using molecular beam sampling mass spectrometry and microprobe sampling with chemiluminescent analysis and (c) OH profiles obtained by absorption spectroscopy using an OH resonance lamp. Several flame studies (4) have demonstrated the applicability of partial equilibrium in the post reaction zone of low pressure flames and therefore the (OH) profile can be used to obtain the (0) profile with high accuracy. 

Vibrational product state distributions have been obtained for reactions studied in crossed molecular beams using the technique of beam electric resonance spectroscopy [109]. This method uses the focusing action of electric quadrupole and dipole fields to measure the radio frequency Stark spectrum of the reaction products, which must possess a dipole moment. This has restricted this technique to reactions producing alkali halides. 

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