Experimental Methods for the Determination of Transition Probabilities

The previous section has shown that the spontaneous lifetime of an excited 

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) 

From measurements of the spontaneous lifetime together with the determination of the relative intensities different transitions 

Since lifetime measurements represent important contributions to the determination of absolute transition probabilities, several experimental techniques were developed before the invention of lasers. For a recent review, see [2.13]. The introduction of pulsed or mode-locked lasers has greatly enhanced the experimental capabilities. Because of their high intensity and the short pulse duration, the sensitivity and the time resolution have been greatly improved and lifetimes in the picosecond range can now be measured accurately. Some commonly used techniques of lifetime measurements with lasers will be discussed in Sect.11.2. 

Besides lifetime measurements the experimental investigation of absorption or dispersion of spectral lines can be used to obtain transition probabilities. According to (2.64) the absorption coefficient integrated over the line profile of an absorbing transition E. E  

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In this section we discuss some experimental methods for the determination of transition probabilities, while in Sect.2.9, we give a survey of the quantum mechanical description of transition probabilities and a brief discussion of some calculational methods. 

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