Resonance trapping

A far-off resonance trap (FORT), in contrast, uses tire dipole force ratlier tlian tire spontaneous force to confine atoms and can therefore operate far from resonance witli negligible population of excited states. A hybrid MOT/dipole-force trap was used by a NIST-Maryland collaboration [26] to study cold collisions, and a FORT was... 

The major piezoelectric applications are sensors (pickups, keyboards, microphones, etc.), electromechanical transducers (actuators, vibrators, etc ), signal devices, and surface acoustic wave devices (resonators, traps, filters, etc ). Typical materials are ZnO, AIN, PbTiOg, LiTaOg, and Pb(Zr.Ti)03 (PZT). 

Fig. 1. A schematic diagram of the relationship between adiabatic potential curves and reactive resonances, (a) shows the conventional Feshbach resonance trapped in a well of an adiabatic curve, (b) illustrates barrier trapping, which occurs near the energy of the barrier maximum of an adiabatic curve.

Since chemical reactions usually show significant nonadiabaticity, there are naturally quantitative errors in the predictions of the vibrationally adiabatic model. Furthermore, there are ambiguities about how to apply the theory such as the optimal choice of coordinate system. Nevertheless, this simple picture seems to capture the essence of the resonance trapping mechanism for many systems. We also point out that the recent work of Truhlar and co-workers24,34 has demonstrated that the reaction dynamics is largely controlled by the quantized bottleneck states at the barrier maxima in a much more quantitative manner than expected. 

The quenching of H(2P) atoms by small molecules has been studied extensively by Phillips et al. (1021-1023) and by Tanaka et al. (583, 960). The quenching rate constant ranges from 10 8 [Shukla et al. (874)] to 10 12 [Wauchopet al. (1023)] cm3 molec-1 sec-1 both for N2 and 02. The discrepancy is partially due to resonance trapping of the 1216 A line in the optically thick system. In the optically thin system the value is about 10-9 cm3 molec- 1 sec-1 [Braun et al. (142)]. The reaction of H(2P) atoms with H2 appears to produce three ground state H atoms [Van Volkenburgh et al. (992)]. The reactions of H(2P) atoms with 02 and N2 yielded electronically excited OH and NH [Wauchop and Phillips (1022)], respectively. 

Figure 3.1 A schematic diagram showing the relationship of reactive resonances to the vibrationally adiabatic potential curve. The upper panel illustrates a Feshbach resonance trapped in a well the lower panel shows a barrier resonance or QBS.

One important class of exceptions to the preceding discussion is provided by prereactive or postreactive van der Waals (vdW) complexes. The lifetimes for such resonances can be much longer than that for conventional transition state resonance trapped near the saddle point. In the discussion of the F+HCl reaction below, we shall see that resonances of this sort can have lifetimes much longer than the rotational period of the complex and thus may show INR signatures. 

Fig. 5.6 Resonance trapping of electrons (positrons) having excess kinetic energy in the gas and liquid phases.

Electron Spin Resonance. Trapped free radicals in irradiated starch were studied utilizing an electron paramagnetic resonance instrument (Varian Associates Type 4500) fitted with a 100-kc. field modulation, Hi-lo power microwave bridge, and a multipurpose specimen cavity. The instrument is stated to have an accuracy of 10% and a minimum resolution of about lO spins per cc. Variants 0.1% pitch mixed with potassium chloride calibration standard containing 10 " spins per cm. of length was used as the reference curve. Samples and standard were contained in quartz tubes, 4 mm. in i.d., in sufficient depth to fill the cavity. 

Ion-cyclotron resonance Trapping of ions in cubic cell under influence of trapping voltage and magnetic field. Orbital frequency related inversely to m/z value. 

As a final example we look at the role of shape resonances In the photolonlzatlon of C2N2 (44). The possibility of shape resonant trapping in this molecule can be quite Interesting due to the C = M component and the C—C bond. Some line source studies (45) and synchrotron radiation measurements (46) of these cross sections have been carried out for photon energies below 24 eV. The CMSM has also been used to study both the photolonlzatlon cross sections and... 

Gomes, R.S. (1995), resonance trapping and evolution of particles subject to Poyinting-Robertson drag Adiabatic and non-adiabatic approaches. Cel. Mech. Dynam. Astron. 61, 97-113. 

An ion trap is a device where gaseous ions can be formed and/or stored for periods of time, confined by electric and/or magnetic fields. There are two commercial types of ion traps in use in MS, the quadrupole ion trap (QIT) and the ion cyclotron resonance trap (ICR). 

The precursor ion selection, fragmentation, and product ion analysis can be separated in space or in time, as shown in Figure 1.29. Separation in time requires trapped ions, as available in the quadrupole ion trap or the ion cyclotron resonance trap. Separation in space necessitates at least two physically distinct mass analyzing devices, one for precursor ion selection (MS-1) and one for product ion analysis (MS-2). The simplest in-space tandem instruments are the triple quadrupole mass spectrometer (QqQ), the double-focusing sector tandem mass spectrometer (EB or BE), and the reflectron time-of-flight mass spectrometer. In a triple quadrupole, the first and third quadrupoles (Q) are mass analyzers, while the center quadrupole iq) serves as the collision cell. In sector instruments, a collision cell is situated... 

We consider spinless polar molecules in the electronic and vibrational ground state In the following, we are interested in manipulating the rotational states of the molecules using dc and ac electric fields and in confining their motion using a (optical) far off-resonance trap (FORT). The application of these external fields will serve as a key element in engineering effective interaction potentials between the molecules. 

Holt and Pipkin observed the 567.6-nm and 404.7-nm photons emitted in the 9 P,-7 S -6 Po cascade of the zero nuclear spin isotope Hg of mercury. The relevant transitions are shown in Figure 8, from which it can be seen that the final cascade level is not the ground state of the atom. Thus in this experiment no precautions had to be taken to avoid the effects of resonance trapping. 

Finally, it should be noted that some criticisms have been made of the experiments using a high-density calcium source on the grounds that there may have been significant effects due to resonance trapping. However, these criticisms have been countered by Aspect and Grangier. ... 

Use low-pass filters on all supply leads and wires coming into the output and input compartments. Use resonant traps for particular frequencies. 

The primary cause of resonant trapping is the beating between the orbital frequency of the body being acted upon and that of the perturber. The phasing of the perturbation produces an acceleration for a portion of the orbit and a compensating deceleration elsewhere in the orbit. 

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