51 



ture and does not occur at the temperature of dry ice (which is 

 about 100°C higher than that of N2) . Debye and Edwards ascribe 

 the phosphorescence to the ejection of an electron which is tempo- 

 rarily caught in a "hole," the light emission being due to the elec- 

 tron's return to its original ground state. 



PERTURBATIONS 



A watery rhodamin solution has a reddish color as compared 

 with the orange color of a methanol solution. The spectroscope 

 shows that in water both the absorption and emission spectrum are 

 shifted by 50 m/x towards the longer wavelength. Evidently, this 

 shift is connected with the higher dielectric constant of water and 

 the difference between the two solvents would be still bigger if, 

 instead of methanol more nonpolar solvents could be used. This, 

 unfortunately, cannot be done because in such solvents rhodamin 

 forms a colorless internal lactone and the lactone formation makes 

 resonance impossible and so eliminates the color (Lundgren and 

 Ninkley). 



What lends interest to this observation is that a similar shift 

 towards the longer wavelength could be observed if to the methan- 

 olic solution of the dye were added small amounts of various 

 substances known to have a strong biological activity. One can 

 expect energy levels in biological systems to be tuned rather care- 

 fully and so a similar shift in energy levels in vivo may disturb the 

 good working order. 



A number of various substances have been tested by McLaughlin 

 (unpublished) for their ability to shift the spectrum of a methan- 

 olic rhodamin solution towards the longer wavelength. The sub- 

 stances have been applied in three different concentrations, 0.01, 

 0.001, and 0.0001 M. The results are summed up in Table I 

 where the numbers mark the shift of the absorption spectrum to- 

 wards the longer wavelength in A. Since acids (1-4) cause a 

 strong shift, all acid substances have been used as neutral sodium 

 salts. 



