Radiative lifetimes for

Fleninger M, Fenistein S, Durup-Ferguson M, Ferguson E E, Marx R and Mauolaire G 1986 Radiative lifetime for v = 1 and v = 2 ground state NO" ions Chem. Phys. Lett. 131 439-43... 

EXAMPLE 5.3 Radiative lifetimes for electric dipole and magnetic dipole transitions. 

Spin Orbit Energies of the 2P% States of the Halogen Atoms and Mean Radiative Lifetimes for Magnetic Dipole Emission (following Garstang13)... 

Phosphorescence corresponds to a different relaxation process. After the absorption phase, corresponding to the transfer of one electron into the Si level (singlet state), a spin inversion can occur if vibrational relaxation is slow, leading the electron to a T, state (triplet state) that is slightly more stable. Flence, return to the ground electronic state will be slower because it involves another spin inversion for this electron. For this reason, radiative lifetimes for phosphorescence can be up to 108 times greater than for fluorescence. 

Arnold et al.24 have calculated radiative lifetimes for the various collision complexes of singlet molecular oxygen on the basis of a collision time of 10"13 sec. The data for wavelengths and transition probabilities are presented in Table III. A recent paper25 describes the theory of double electronic transitions, and gives calculated oscillator strengths for the oxygen systems. 

The radiative lifetime for the 52IIr state has been measured by Jeunehomme and Duncan,222 who produced the state by electron impact. For the radiative step... 

Whether the singlet is a (n, jr ) state or an ( , it ) state can be established from solvent effect. A blue shift in polar solvent suggests an (n, 7i ) state, a red shift a (tc, tc ) state. A rough guess can be made from the radiative lifetime for fluorescence which is of the order of 10-5 s for biacetyl. Hence, it appears that the lowest excited singlet is an Sx (n, n ) state. From dilute solution value of f, we find that only 1 % of the initially excited molecules are capable of emission with a rate constant 1 x 105 s-1 == 1/t . Therefore 99% of the molecules must be transferred to the triplet state, assuming S S do not occur. The rate constant for... 

J. Oddershede, N. Elander, Spectroscopic Constants and Radiative Lifetimes for Valence-Excited Bound States, J. Chem. Phys. 56 (1972) 3495. 

Regarding the latter issue, it has to be noticed that for the phosphorescence decay of isolated ligands, the values for rr may be in the ms to sec time range or longer [16]. For the complexes, the heavy atom effect may cause singlet-triplet mixing to an extent that a formal 3LC level exhibits tr as short as tenths of xs [1]. Consistent with this, we shall see later that radiative lifetimes for 3LC emitters of the Ir(III)-polyimine family are tr 50 xs or larger (kt 0.2 x 105 s-1 or smaller, Eq. 2). 

It is possible to calculate other spectroscopic details for the 4f" 15d and 4F configurations. For example, radiative lifetimes for Eu2+ typically increase with temperature, rather than... 

Selected values of radiative lifetimes for Ln111 ions... 

Moreover, the radiative lifetime is not a constant for a given ion and a given electronic level. Indeed, there is a dependence on the refractive index, as clearly shown by eq. (14), so that transposition of a literature value to a specific compound cannot be made directly, which explains the wide range of rrad values reported for an individual Lnm ion. As an example, reported radiative lifetimes for Er111 range from 3 to 12 ms, even for relatively similar compounds (see table 19 below) Another hypothesis inherent to Judd-Ofelt theory is that 4f functions do not contain contributions from 5d orbitals, which is not quite the case for Pr111 and Tbm for instance. Selected data reported in the literature are listed in table 5. 

The main results obtained from this study were the g-factor and the radiative lifetime for the G state. However, the experimental techniques developed proved to be very powerful in the study of other electronic states of H2, as we will see shortly. 

Julienne has used the calculated transition dipole moment function to obtain the radiative lifetimes for the j +... 

LIF of SiHF formed by reaction of SiH4 with Fj. Radiative lifetime for the first vibronic state... 

It is not possible to separate the photochemistry of 1,3-cyclohexadiene from that of 1,3,5-hexatriene, its major product, since the latter absorbs radiation in the same region of the spectrum and even more intensely to revert to 1,3-cyclohexadiene. The ir- - w absorption of 1,3,5-hexatriene shows considerable vibrational structure. The radiative lifetimes for the singlet states of both 1,3-cyclohexadiene and 1,3,5-hexatriene can be calculated to be less than 10 sec. The lowest triplet state of trans-1,3,5-hexatriene has been placed at 47 kcal./mole, and a second triplet state may lie at approximately 14 kcal./mole above that. These values were also obtained by direct singlet — triplet excitation. 

If the spontaneous emission of radiation of the appropriate energy is the only pathway for a return to the initial state, the average statistical time that the molecule spends in the excited state is called the natural radiative lifetime. For an individual molecule the probability of emission is time-independent and the total intensity of emission depends on the number of molecules in the excited state. In a system with a large number of particles, the rate of decay follows a first-order rate law and can be expressed as... 

Figure 1. Comparison of the theoretical radiative lifetimes for different rotational levels of the v = 0 level of the state of OH (dashed line) with the high-frequency deflection...

The Nj ion, which is isoelectronic with CN, has similar B2E+ A2II perturbations. Dufayard, et al., (1974) have measured radiative lifetimes for individual... 

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