I have a Dahlmann in my background. A Luise Theodore Ernestine Dahlmann, born about 1857, Frankfurt/Main, was the second wife of my ggrandfather, Professor Joseph Rawson Lumby, Cambridge University, England. (I am the descendent of him and his first wife).Luise Dahlmann was the grandaughter of Professor Christoph Friedrich Dahlmann, b. 13 May 1785 in Wismar, Mechlenberg, Germany. He d. 5 Dec.1860, Germany. Pr. C.F. Dahlmann was most noted for being the leader of the "Group of Seven" at the University of Göttingen. They were the rebels. In this group were the Gebrüder GRIMM of Fairy Tale fame. I believ about 3 years ago there was a monument unveiled commemorating this group of seven in either Hanover, or Bremen.
Is this of any help to you ?
If you have any info about the descendents of Christoph Friedrich, who had three sons (all unknown) who was a Direktor des Landgerichts and a Judge of the Appeal Court in Marburg, Germany, I would certainly appreciate it.