Vibration→Rotation Energy Transfer in Hydrogen Chloride

Chen, Hao‐Lin; Moore, C. Bradley

doi:10.1063/1.1675468

Cited by 171 publications

(14 citation statements)

References 19 publications

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“…HCl is a polar diatomic molecule with a vibrational modeν HCl = 2886 cm −1 . The spectroscopic properties of HCl required to understand the relaxation effects are described in [15][16][17][18] and rovibrational energy transfer processes in HCl-O 2 /N 2 /He are also discussed in a series of papers [19][20][21][22]. In addition, the relaxation rates for different reactions are summarized in Table 2.…”

Section: Molecular Relaxationmentioning

confidence: 99%

Molecular relaxation effects in hydrogen chloride photoacoustic detection

Besson

Schilt²,

Thévenaz

2007

Appl. Phys. B

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A photoacoustic (PA) sensor has been developed to monitor hydrogen chloride at sub-ppm level in the 1740-nm region. The system was designed to control the process in the novel low-water-peak optical fiber manufacturing process. Relaxation effects in hydrogen chloride PA detection in oxygenhelium and nitrogen-helium gas mixtures are presented, showing that the generation of the PA signal is strongly affected by the ratio of these substances. In addition, the role of water vapor in the PA signal is investigated. Photoacoustic spectroscopy (PAS) is a widely recognized technique for its high performance in the detection of trace gases in various applications [1][2][3]. The main advantages of this technique are its intrinsically zero background nature and its achromaticity, which result in a very sensitive and simple setup arrangement suitable in a broad spectral region ranging from the ultraviolet to the mid infrared.The development of photoacoustic (PA) sensors operating in the near-infrared (NIR) range has strongly increased in recent years due to the excellent properties of the available diode lasers. Such laser sources provide single-mode emission (for instance distributed feedback (DFB) lasers) with narrow line width (typically a few MHz), an output power ranging from a few mW to several tens of mW, modulation capabilities and thousands of hours of operation. Moreover, their compact size and their fiber-coupled output make them easy to align with the PA cell.Despite its above-mentioned advantages, PAS is an indirect method since the optical energy absorbed by the molecules is detected through an acoustic wave generated in the gas due to thermal expansion resulting from the vibrationto-translation (V-T) relaxation of the excited molecules. Consequently, the conversion from optical to thermal energy depends on the physico-thermal properties of the gas, so that a calibration of the sensor is required. Whereas molecular re-

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Section: Molecular Relaxationmentioning

confidence: 99%

Molecular relaxation effects in hydrogen chloride photoacoustic detection

Besson

Schilt²,

Thévenaz

2007

Appl. Phys. B

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“…Our description follows Moore (28) and Chen and Moore (27). At thermal equilibrium at ordinary temperatures both the HCl and DCl molecules are very predominately in their ground, ϭ 0, vibrational state but we take it as given that the system can be pumped away from equilibrium by rapidly raising the concentration in the ϭ 1 state of HCl or of DCl molecules or of both.…”

Section: Kineticsmentioning

confidence: 99%

“…1, where the concentrations [HCl( ϭ 1)] and [DCl( ϭ 1)] are plotted vs. Pt, where P is the pressure in torr and time is in sec. As discussed by Chen and Moore (27), the concentration of HCl and of DCl in the ϭ 1 state is monitored through their slow emission in the IR, an emission that is too slow to significantly deplete the concentration but is sufficient for detection.…”

Section: [2]mentioning

confidence: 99%

“…It, too, will relax on its own. But following Chen and Moore (27,28) we use a mixture of HCl and DCl. The two systems are then strongly coupled by the one quantum exchange process…”

mentioning

confidence: 99%

“…The kinetics of the HCl/DCl mixture were thoroughly studied (27,28) by using an HCl laser to pump the HCl molecules in the gaseous mixture to the ϭ 1 state. In the numerical example shown in Fig.…”

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Quasiclassical computation

Remacle

Levine

2004

Proc. Natl. Acad. Sci. U.S.A.

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The chemical kinetic description of time evolution where the phase is random but the states are discrete is discussed as a basis for a computational approach. This proposed scheme uses numbers in the entire range of 0 to 1 to represent Boolean propositions. In the implementation by chemical kinetics these numbers are the mole fractions of different species. Vibrational relaxation in a mixture of HCl and DCI is the physical system that is used to illustrate the approach. Energy exchange in such a mixture corresponds to two strongly coupled two-level systems. A search problem, previously discussed in the quantum computing literature, is solved as an example. The solution requires the same number of function evaluations as in the quantal case. The action of the oracle is described in detail.T he basic element of current logic devices is a switch. It is either on or off. This corresponds to the two possible values, say 0 and 1 or true and false, of a Boolean variable. The values of physical observables are not usually either 0 or 1. A molecule is not easily made to act as a switch. On the other hand, molecules exhibit a rich dynamical behavior that we would like to take advantage of so as to perform logic operations.In this article we focus on what is, to us, a rather common characteristic of molecules. It is that molecules can be classified into discrete alternatives. The simplest such distinction is the very idea of a chemical species. The operational definition of a molecule is made possible by the (relative) stability of the entities we know as atoms and by the atoms combining into molecules in simple and definite proportions. Thereby a molecule can be identified to be, say, HCl and not HBr or any other diatomic one. A finer but still operationally fully viable resolution is that molecules of a given chemical species can be identified to occupy definite quantum states (or groups of states). Except for special circumstances it is typical of molecules that the quantum mechanical phase of its states is random. So the different states of molecules act as discrete and mutually exclusive classical alternatives. This state of affairs is what we mean by quasiclassical. We want to perform logic operations by taking advantage of the probabilities of occupancy of the different quantum states that are resolvable in an experiment. By the end of this article we intend to show, by an explicit example, that this is possible.To implement our program we need input from several directions. In this introduction we review the different ideas that we intend to invoke. Then we describe a solution of a particular problem with special reference to what is the logic problem that we claim to solve, what is the physical system that is used, and how we set up the interface between them.We do not use the phase of the quantum mechanical state because we propose to operate under conditions where this phase is random. Starting with the work of Deutsch (1, 2), there is an extensive current literature emphasizing the critical computational advant...

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