Photodissociation probability

Lavrich D J, Buntine M A, Serxner D and Johnson M A 1993 Excess energy-dependent photodissociation probabilities for Ot in water clusters O, I 1i Chem. Rhys. 99 5910-16... 

From the three decay times, which each measurement provides, the main point of interest how is the type I quantity T. It characterizes the dynamics of the relevant electronic state of the cluster size under investigation. The data, therefore, allow us to determine directly the photodissociation probabilities 1/r 1 of the observed clusters excited at the energies of the photon irradiation. The corresponding results reflect the stability of the clusters, as graphically presented in Fig. 26. For all measured cluster sizes the fragmentation probabilities at E = 2.00 eV are smaller than those for the other photon energies (figs. 26a, b). For E = 2.00 eV and E = 2.94 eV the curves of the dependence of the photodissociation probability on the cluster size have similar shapes. In Fig. 26b both curves show a particular instability for Kg, which... 

The photodissociation probability into the state characterized by n at energy E, Pn(E i), is given by the square of Aa(E i), the photodissociation amplitude for observing the free state exp(—iEt/1i) E, n 0) in the long-time limit. That is,... 

Here Pq(a) and Pq(b) are the independent photodissociation probabilities associated with routes a and b, respectively, and Pq(ab) is the interference term between them, discussed below. 

That is, control over the enantiomer ratio is lost upon m summation, both channels q—D and q = L having equal photodissociation probabilities. 

The state-specific photodissociation probability, Pn(E) [Eq. (2.74)], is the long-1 time probability, at fixed energy E, of observing a particular internal state [n) of the dissociated fragments. Hence, using Eqs. (10.5) and (10.6), we have that... 

Here ] ), IV)) = [2J,) IV)), where [ , ) is abound state ofHu [defined in Eq. (2.1)]. and Nj) denotes a free radiation state with Nt photons in the Iq mode, whose frequency is a>j. The molecule then interacts with the field, and we are interested in determining the photodissociation probability, defined as the probability of eventually t -> oo) populating an eigenstate of Hr, where the molecule is dissociated. [Strict )... 

Following our strategy in the weak-field domain (see Chapter 3), we do not obtain. the photodissociation probability by actually following the dynamics for long times. 

I ppie cw rate of transition R(E, n, N i, A, -), into the radiatively decoupled state lpjflT, N), can be obtained as the rate of change of the photodissociation probability as the interaction is being slowly switched on ... 

A new method, based on that of Griess-Saltzman, has been developed for measuring N02 in the atmosphere.160 A detailed study has been made of the relative quantum yields for the photolysis of N02 to NO at 5 or 10 nm intervals in the range 295—445 nm, and also at longer wavelengths. The photodissociation probability of N02 remains close to unity for photolysis by all wavelengths shorter than the dissociation limit at 398 nm.161 The photolysis of low concentrations (0.9—lOOp.p.m.) of N02 in air has been investigated and the rate constants of three of the elementary reactions have been directly determined.162... 

Table 1. Photodissociation probabilities[20] for C I- CFa+I with laser frequency of co=40323cm . For more details see Refs 18 and 14. RM=R matrix, LD=Log-derivative methods.

While the dipole absorption features [114, 124] and photodissociation dynamics of small sodium clusters are rather well known [112, 113, 126, 127, 407-409], there is very little knowledge about potassium clusters larger than the dimer. The lack of experimental data might be caused by ultrafast fragmentation processes within the potassium clusters, so that conventional stationary spectroscopic techniques might fail. Hence, the goal of this section is to determine the photodissociation probability of small potassium clusters as a function of cluster size as well as excitation energy. 

The primary photodissociation probably occurs from high vibrational levels of the electronic ground state reached by rapid intersystem crossing directly from the originally excited Bg state. No evidence was found for collisional deexcitation, and the dissociation via reaction (4) occurred with a quantum yield close to unity. Some molecular dissociation Into N2 and H2 can not be excluded, because this process Is symmetry-allowed for C/S-N2H2 [1, 12]. The successive fission of the NH bonds is predicted from ab Initio SCF Cl studies to be the preferred pathway in the photolysis of C/S-N2H2 [13, 14]. The photolytic decomposition into N2 and H2 was already observed earlier in a few qualitative experiments at very low pressures (< 0.1 Torr) [9]. 

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