Ladder climbing

The theoretical model developed to explain these experiments is based on inelastic tunneling of electrons from the tip into the 2ir adsorbate resonance that induces vibrational excitation in a manner similar to that of the DIMET model (Figure 3.44(b)). Of course, in this case, the chemistry is induced by specific and variable energy hot electrons rather than a thermal distribution at Te. Another significant difference is that STM induced currents are low so that vibrational excitation rates are smaller than vibrational de-excitation rates via e-h pair damping. Therefore, coherent vibrational ladder climbing dominates over incoherent ladder climbing,... 

Due to Eq. (A.3) the above theories only permit the excitation of one quantum of vibration at a time (b and b+ connect vibrational states where their populations differ by only one quantum). This is a consequence of the linear approximation because the nuclear coordinates deviate slightly from the equilibrium situation the molecule can only change its vibrational state by the smallest of the allowed quantities one quantum. In order to account for the excitation of several quanta at a step (coherent excitation) one needs to use other kind of theories (see for example [24]). Nevertheless, the presented approaches permit the sequential excitation of quanta in a ladder climbing fashion (incoherent excitation). 

Other studies of CO loss from small molecules include the photolysis of OCS on Ag clusters, in which an odd-even dependence on the number of Ag atoms in the cluster was discovered. OCS desorbs non-dissociatively from even numbered clusters, but dissociates to CO and AgnS on odd numbered clusters. This alternation correlates with the ionization potentials of the naked metal clusters, and the photoreactivity pattern can be explained in terms of a charge-transfer mechanism. A numerically efficient algorithm has been developed in the theory of ladder-climbing and IR multiphoton dissociation, and has been applied to HCO. ... 

The possible additional contribution of a ladder climbing vibrational mechanism to the rate of dissociation is however incompatible with the presence of a high concentration of oxygen atoms, as discussed in Sect. 3.2.1. 

One might expect that linearly chirped pulses are sufficient to ladder climb Morse potentials, because the slope of the chirp can be adjusted to match the anharmonic spacing of the Morse potential (the frequency difference between... 

The experimental species recommended by OECD guidelines is the adult domestic hen. During the tests the animals are to be observed for behavioral abnormalities, locomotor ataxia, and paralysis. Twice a week the animals are subjected to a period of forced motor activity (ladder climbing). Animals that show signs of neurotoxic effects are sacrificed and examined by gross necropsy and histopathologically. 

These arguments can be applied to ladder-climbing collisions, which are responsible for canning vibrational energy to higher levels in both polyatomics and diatomics. For example in CH3F the event ... 

The rate coefficients for dissociation from different vibrational levels have been studied much less widely than for vibrational energy transitions. Two models are commonly used for calculations the ladder-climbing model assuming dissociation only from the last vibrational level (see, for instance, Armenise et al. (1996 1995) Capitelli et al. (1997) Osiprov (1966)), and that of Treanor and Marrone Marrone Treanor (1963) allowing for dissociation from any vibrational state. 

In the frame of ladder climbing model, the rate of dissociation is specified by the number of molecules occurring on the last vibrational level. Consequently, the dissociation rate is totally specified by the probabilities for the vibrational energy transitions to the last level. In the case when dissociation can occur from any vibrational level, the expression for the rate coefficient for dissociation of a molecule on the vibrational level i can be written in the form Nagnibeda Kustova (2009) ... 

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