A pulsed HCl chemical laser is used to excite HCl molecules vibrationally in the presence of Br atoms in a discharge-flow reactor. The rate of the reaction Br +HCl(v)-^ HBr + C1 increases by a factor of lO*' at room temperature if HCl(t; = 0) is excited into v~2, Excitation occurs predominantly for tf^Cl. CI atoms generated by the laser-stimulated reaction react with Brg to form BrCl, which is detected by time-resolved mass spectrometry and shows an enrichment of ^^Cl (90% ^^Cl).Molecules formed in simple exothermic chemical reactions of free atoms often exhibit a strong vibrational and rotational nonequilibrium excitation/ which may sometimes be converted into stimulated infrared emission.^ ^ Microscopic reversibility requires that such reactions will proceed in the endothermic direction more rapidly when the activation energy is deposited in internal-energy modes of the reacting molecules.In this Letter, we report the direct observation of selective stimulation of the endothermic exchange reaction Br + H^^Cl-HBr+3^Cl,using the emission from a pulsed HCl chemical laser. After excitation of HCl(f =0) to f =2, the reaction rate increases at room temperature by a factor of 10^^. The experimental conditions are chosen so that the chemical reaction can compete with energy-transfer processes.^ The experiments were performed using an arrangement shown in Fig. 1. The HCl laser is similar to that described by Airey.^ Laser pulses 10"^ sec in duration (pulse energy typically 10"^ J) were used to excite HCl vibrationally in the presence of Br atoms in a discharge-flow reactor (Pyrex tube, 2 cm diam, 20 cm length; flow velocity 30-70 m/sec). Reaction products were analyzed using a molecular-beam-sampling system and a quadrupole mass spectrometer. Br atoms were generated in two parallel microwave discharges by dissociation of Br2 diluted in He. Absolute Br-atom concentrations were mea-FIG. 1. Schematic of the experimental apparatus for mass-spectrometric detection of products from laserinduced chemical reactions. 1597
Both metabolic rate and protein catabolism are known to increase following severe head trauma, but the etiology of this hypermetabolism is unknown. To further investigate the problem, we studied the metabolism of 17 patients with indirect calorimetry who had severe craniocerebral trauma only and who required ICP monitoring for management. Patients were studied daily and immediately after ICP spikes greater than 20 mm Hg, prior to treatment with hyperventilation, osmotic diuretics, or barbiturates. Oxygen consumption (VO2) was correlated with ICP. Two groups of patients were identified. Group I patients were treated with hyperventilation and osmotic diuretics while Group II patients additionally received cerebral metabolic depressants. Group I had a significant correlation coefficient between VO2 and ICP. Significant hypercatabolism early in the post trauma period was demonstrated by increased urine urea nitrogen. Our observations suggest that in patients with craniocerebral trauma, elevated ICP is associated with increased oxygen consumption, protein catabolism and systemic hypermetabolism. Cerebral metabolic depressants blunted increases in VO2 which were seen with elevated ICP.
Der Einfluß einer selektiven Schwingungsanregung auf den Ablauf einfacher neutraler und endoenergetischer Reaktionen in der Gasphase wurde anhand der Reaktionen von HCl(ν) mit H‐, D‐, Cl‐ und Br‐Atomen mit Hilfe der Methode der laserinduzierten Fluoreszenz in einer Strömungsanordnung untersucht. Durch die Bestimmung der absoluten Konzentration der schwingungsangeregten Moleküle, die zeit‐aufgelöste Beobachtung der Atomkonzentration und den massenspektrometrischen Nachweis der Produkte der laserinduzierten Reaktionen über ein Molekularstrahl‐Probenahmesystem war eine direkte Unterscheidung zwischen reaktiven und energieübertragenden Prozessen möglich. Bei einer Laserimpulsenergie von 10 mJ ergibt sich aus dem Vergleich der Intensität der Infrarotfluoreszenz der Zustände HCl(ν = 2) und HCl(r = 1) ein Anregungsgrad von Dieses Ergebnis erhält man auch aus der Messung des Temperaturanstieges von ΔT = 7 K in der Reaktionsmischung nach vollständiger Schwingungsrelaxation von HCl(ν) durch Chloratome. Die Messungen der spezifischen Geschwindigkeitskonstanten k(ν = 1) wurden bei sehr geringem Anregungsgrad ausgeführt. Hierdurch konnte eine Entvölkerung des Zustandes HCl(ν = 1) auf dem Weg über höhere Schwingungszustände vermieden werden. Im einzelnen wurden bei 295 K folgende Ergebnisse erhalten: Der drastische Anstieg der Geschwindigkeit der Reaktion (5) um einen Faktor 1011 nach Schwingungsanregung von HCl(ν) erlaubte eine isotopenselektive Reaktionsführung der Art Die gebildeten BrCl‐Moleküle zeigen eine Anreicherung auf 90% Br35Cl.
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