The following is about habilitation and junior professorships in general, not particularly about physical chemistry.
A few things about junior professorships first:
- Depending on the field, a habilitation is no longer a strict necessity. Having done a successful junior professorship is formally sufficient for a professor position as well. You of course don't know in advance if the hiring committee for the position you will be interested in at some point isn't preferring candidates with a habilitation, though.
- There are nowadays also tenure-track junior professorships. They ensure that if you do good work, you get a permanent professorship afterwards, without the need to have a habilitation. Once you showed that you can do a good job on a permanent professorship, the habilitation should then cease to be important if you apply elsewhere later.
But more importantly:
- There are no designated "habilitation positions" in Germany. Rather, there are positions as "wissenschaftlicher Mitarbeiter" (scientific employee) that you can hold while working towards your habilitation. The possibility to write a habilitation thesis while holding the position may be mentioned in the job advertisement, but is also often not. If you see a position that may be suitable offered somewhere, you will have to ask (the respective professor) if he/she thinks if you should apply as someone interested in working towards a habilitation.
- The important part for writing a habilitation thesis is that you have a position with a perspective to stay for a longer period of time, as necessary for this purpose. A position in a newly started EU starting/consolidator/advanced grant would be suitable, for instance. A "Landesstelle" (not directly attached to a third-party funded project) is suitable, too - but you will have to convince the professor having such a position that giving it to you is a wise investment for him/her.
- Sometimes you see a position for an "Akademischer Rat", which is a permanent somewhat glorified postdoc position and should be suitable for writing a habilitation thesis. These are very rare, though.
Note that positions suitable for habilitation are not always publicly announced, and it's not uncommon to have your current professor/advisor phone up a few colleagues in the area you want to move to in order to check if there are any suitable not yet announced free positions upcoming in their research groups.