Stern-Vollmer plot

A sufficient number of atoms has to be produced to be able to detect a fluorescence signal. On the other hand, when the density of atoms is too large, the collisional quenching interferes with the radiative lifetime. Normally, a Stern-Vollmer plot is drawn and the lifetime extrapolated to zero concentration is taken as the radiative lifetime (Fig. 8.). Extrapolation is simple when using a cell containing the atoms. 

Figure 8. Stern-Vollmer plot for tellurium 7p Pj. Pj state lifetime determination...

Fig. 6.86 Collisional depopulation of the excited level 7 of a molecule and example of a Stern-Vollmer plot for the NaK level v = 1, 7 = 13) depopulated by collisions with...

Measuring the effective lifetime as a function of the exciting radiation intensity and also its dependence on the density of collision partners (Stern-Vollmer plot) allows one to determine the three transition probabilities separately (Vol. 2, Sect. 8.3). 

Fiq.2.2U Inverse effective lifetimes of some excited (v , J ) levels in the iDn state of the NaK molecule as a function of pressure P of the K-atoms (Stern-Vollmer plot)... 

Fig. 12.6. Stern-Vollmer plot showing the dependence of effective lifetime of an excited (v, J ) level in the Blny state of Na2 on the vapor pressure of Na atoms (upper curves) and on the pressure of He added to the vapor cell... 

Here one-photon absorption is used to prepare allyl isocyanide with 5, 6, and 7 quanta in the terminal olefinic (H2C=), nonterminal ole-finic (=CH-), or methylene (-CH2 ) CH stretches. Because of their different frequencies each of these CH stretches can be excited selectively with very little spectral impurity. For a particular overtone the methylene CH stretch contains the least energy and the terminal olefinic CH stretch the most. Unimolecular rate constants were measured by Stern-Vollmer plots, and were found not to agree with RRKM predictions. Though the terminal olefinic CH stretch is most excited for a particular overtone, excitation at this site gives a smaller unimolecular rate constant than does excitation at the nonterminal olefinic CH stretch. This result unambiguously characterizes allyl isocyanide isomerization as intrinsically non-RRKM. 

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