Rovibration excitation spectra

Recently, a similar approach has beep-used to investigate van der Waals complexes of Al( P) with Ar and In( P) with Ar, Kr, and Xe." Laser vaporization of the refractory atom followed by supersonic expansion in rare gas carrier was to sinthesize van der Waals complexes. Gardner and Lester" then used mass resolved resonance-enhanced multiphoton ionization (REMPI) for obtaining rovibration excitation spectra... 

Because dissociation on So is barrierless, the product state distributions should be well approximated by statistical theories, especially when the excess energy is small, as in the Valachovic study. Product state distributions arising from the So pathway should be characterized by small translational energy release, but significant rovibrational excitation of HCO. This signature is demonstrated in the top panel of Fig. 17, which shows a HRTOF spectrum with... 

FIGURE 3. Excitation spectrum of A10(X2l+) from the A1 + O2 reaction at etrans = experimental (a), and calculated (b) with a statistical rovibrational... 

Molecules vibrate at fundamental frequencies that are usually in the mid-infrared. Some overtone and combination transitions occur at shorter wavelengths. Because infrared photons have enough energy to excite rotational motions also, the ir spectrum of a gas consists of rovibrational bands in which each vibrational transition is accompanied by numerous simultaneous rotational transitions. In condensed phases the rotational stmcture is suppressed, but the vibrational frequencies remain highly specific, and information on the molecular environment can often be deduced from Unewidths, frequency shifts, and additional spectral stmcture owing to phonon (thermal acoustic mode) and lattice effects. 

Numerical analysis of the results of studies of SF, excitation in the mode by intense CO2 laser radiation based on a triply degenerate oscillator model t Vibrational overtone spectrum of gaseous SF at 193 K Theoretical study of homogeneous linewidths in SF deduced from experimental IRMPE studies at 944.2 cm . IVR rates and sensitivity to rovibrational distribution... 

BUR/W1L] Burger, H., Willner, H., The high-resolution Fourier transform spectrum of monoisotopic C Se2 in the V2, V3, and Vi + V3 regions equilibrium, ground, and excited state parameters determined by rovibrational analyses, J. Mol. Spectrosc., 128, (1988), 221-235. Cited on page 206. 

Radiometry. Radiometry is the measurement of radiant electromagnetic energy (17,18,134), considered herein to be the direct detection and spectroscopic analysis of ambient thermal emission, as distinguished from techniques in which the sample is actively probed. At any temperature above absolute zero, some molecules are in thermally populated excited levels, and transitions from these to the ground state radiate energy at characteristic frequencies. From Wien s displacement law, Amax T = 2898 fim-K, the emission maximum at 300 K is near 10 fim in the mid-ir. This radiation occurs at just the energies of molecular rovibrational transitions, so thermal emission carries much the same information as an ir absorption spectrum. Detection of the emissions of remote thermal sources is the ultimate passive and noninvasive technique, requiring not even an optical probe of the sampled volume. 

Similar spectral and spatial studies have been performed for the ejecta of stars in the later stages of their life to probe their molecular composition and evolution. Because the central star heats the gas to warm temperatures (up to 1000 K), rotational lines in the far-infrared can be excited as well. Figure 3 shows the far-infrared spectrum of such a star, IRC 10216, obtained by the Infrared Space Observatory. For these objects, molecules can also be detected through their rovibrational transitions against the bright far-red, and near- and mid-infrared continuum of the star. 

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