Quasibound molecules

The Chu experiment produced quasibound molecules from Raman-cooled Cs atoms, but other experiments have been able to form cold molecules directly from atomic Bose-Einstein condensates. The Ketterle group at MIT accomplished Na2 formation from a Na BEC with an... 

V. Engel Let me come back to the distribution of lifetimes of the ZEKE Rydberg states. I wonder if there is a simple picture behind. Consider a much simpler molecule, namely the Nal molecule Prof. Zewail told us about. There you have a bound state coupled to a continuum. It can be shown that in such a system the lifetimes of the quasibound states oscillate as a function of energy. In fact, Prof. Child showed with the help of semiclassical methods that there are lifetimes ranging from almost infinity to zero [1]. That can be understood by the two series (neglecting rotation) of vibrational levels obtained from the adiabatic and diabatic picture. If two energy levels of different series are degen-... 

We show how one can image the amplitude and phase of bound, quasibound and continuum wavefunctions, using time-resolved and frequency-resolved fluorescence. The case of unpolarized rotating molecules is considered. Explicit formulae for the extraction of the angular and radial dependence of the excited-state wavepackets are developed. The procedure is demonstrated in Na2 for excited-state wavepackets created by ultra-short pulse excitations. 

A vibration rotation level of a diatomic molecule which lies above the lowest dissociation limit may be quasibound and able to undergo spontaneous dissociation into the separate atoms. This process is known as predissociation, and two different cases may be distinguished for diatomic molecules, as we will see shortly. Predissociation does not normally play an important role in rotational spectroscopy but merits a brief discussion here for the sake of completeness. 

Second, being quasibound Inside a potential barrier on the perimeter of the molecule, such resonances are localized, have enhanced electron density In the molecular core, and are uncoupled from the external environment of the molecule. This localization often produces Intense, easily studied spectral features, while suppressing non-resonant and/or Rydberg structure and, as discussed more fully below, has a marked Influence on vibrational motion. In addition, localization causes much of the conceptual framework developed for shape resonances In free molecules to apply equally well to photolonlzatlon and electron scattering and to other states of matter such as adsorbed molecules, molecular crystals, and Ionic solids. 

Figure 2. Schematic of the effect of a potential barrier on an unbound wave function In the vicinity of a quasibound state at E E (adapted from Ref. 18). In the present context, the horizontal axis represents the distance of the excited electron from the center of the molecule. Reproduced with permission from Ref. 18. Copyright 1974, Academic Press.

Hydrogen-bond lifetime analysis revealed that HBs between the polar head groups of the micelle and the water molecules are much stronger than those between two water molecules in bulk water and thus exhibit much slower dynamics - almost 13 times slower than that of bulk water. This result indicates the presence of quasibound water molecules on the surface. 

ABSTRACT. Previous theoretical and experimental work on the ions H+ and HD+ is reviewed. Earlier work using ion beam techniques to study the uppermost bound levels and quasibound levels of H+ is discussed, and a suitable model for the molecule in these levels is proposed. Earlier work using ion beam techniques to study the vibration-rotation levels of HD+ is reviewed. 

FIGURE 3.16 Adiabatic potential and the wavefunctions of the quasibound levels B and E shown in Figure 3.15 as functions of the atom-molecule separation. Amplitudes of the wavefunctions have been reduced by a factor of 10 for the convenience of plotting. (From Balakrishnan, N., J. Chem. Phys., 121, 5563, 2004. With permission.)... 

Examination of individual trajectories for the modified LEPS surface reveals reaction of vibrationally excited bound or quasibound I2 with H2 through the nearly collinear configuration I-H-H-I. With the slowly moving I2 molecule stretched to an internuclear distance of about 5 A, the H2 molecule approaches from the side and inserts between the two atoms. The H atoms separate and as the I atoms move apart one H atom goes with each. The reaction of I -h I with H2 is revealed to be almost identical. As the slowly moving I atoms pass by each other at a distance of about 5 A, the H2 molecule approaches firom the side and inserts between the two atoms. The H atoms separate and as the I atoms move apart one H atom goes with each. Thus, the bimolecular reaction H2 + l2(hi v) HI + HI is not much different from the termolecular reaction H2 + I + I — HI + HI. 

Species trapped in one of these states are defined as van der Waals molecules. Those trapped by the centrifugal barrier in quasibound states are called metastable van der Waals molecules. There are of... 

The rate constants and averages in Figs. 4-9 and Table 7 all refer to bound rearranged products. Only two of the initial states considered lead to any quasiboundrearranged products these are the 5,24 state, which is itself quasibound, and the 10,12 state, which is barely bound. The 5,24 state has only a small rate constant, 1.0 0.7 X 10 cm molecule"" s"", for producing rearranged quasibound products the 12,10 state has a larger rate constant for quasibound-state production, 1.3 0.4 x 10" cm molecule " s, most of which corresponds to final state (12,11). 

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