Broadening and Shift of the Second Doublet of the Rubidium Absorption Series Under Different Pressures of Argon and Helium

The shift and broadening of the second doublet of the principal series of rubidium produced by argon and by helium were studied for pressures up to 123.5 atmospheres (rd 52) and up to 97.5 atmospheres (rd 44), respectively. The red shift produced by argon gives a linear relationship with its relative density, rd. The slopes for both components of the doublet are 2.95 cm^-1/rd. The violet shift produced by helium in the high pressure range is greater than linear with the rd. The ²P1/2 component is shifted more than the ²P3/2 component.Argon shows a nicely linear broadening for both components over the entire range of rd. For the ²P3/2 component the broadening is 2.28 cm^-1/rd and for the ²P1/2 component it is 2.11 cm^-1/rd. Helium appears to give a definite quadratic broadening, particularly for the ²P3/2 component.