Tenured position to be started very soon...what to do with the old affiliation Nowadays I am a second year assistant professor (without tenure) in physics at a German university (rank W1, Juniorprofessor), advising 2 PhD students.

Today, it came to me the information about a permanent position abroad (in Europe) and I am strongly considering applying for it. 

My problem is the following: the selection process had just started now, and I will not know the decision until middle july. The preference in the new institution is to start the new position is September 2015 (which means that between the decision and the start is less than 1,5 months).

My questions are the following:


At which point should I say something about this to my present institution: of course I do not know if I will be selected for the position, but I also understand that it is very bad for my present institution now to say them: "Well, I will leave the institution in one month."
At which point should I explain my Phd students about this change: this is definitely my most important headache. How should I present this point to them, and more important - when? Do you think it is good that I tell them that I want to apply for this position?
I would not tell anyone anything until you have accepted the position (ideally with a signed contract). Leaving a position on short notice leaves your colleagues in a bind to cover your teaching and leaves your graduate students (and possibly lab personnel) at risk. If you are given an offer, you may be able to negotiate solutions to these problems (or the offer may be made so late, that it is not an issue). It is not unheard of for graduate students to be allowed to transfer. Delaying the start date by a semester, even a year, is not uncommon. If the start date is not flexible, you may also be able to negotiate some sort of teaching buyout which will allow you to teach a reduced load at both universities for a semester/year with each university covering a portion of your salary.

The reason not to tell people is two fold. If the position falls through, you do not want to upset your colleagues. Telling your students also seems premature. They really little to no control over the situation and it is likely going to make them anxious.

In terms of control, the student can drop out immediately. By telling them early, you save them 2 months of "wasted effort". They can also work harder with the goal of graduating early. The 2 months additional warning time is not going to result in a significantly quicker graduation. Arranging alternative supervision is really out of the hands of the student and requires the current supervisor, the new supervisor, the department, and the funder all agreeing. They are not going to move quickly on the issue until the PI confirms he/she is leaving.

Not telling the student is not the same thing as not preparing the student. Hopefully, when you took the student on, you created a safety net for them (e.g., a second supervisor and alternative research paths). You should reconsider this safety net, alternative supervision, the key resources they need, and the time lines of their current and future projects. It is probably worth discussing aspects of the safety net and steering them into now (e.g., increased collaborations with a potential second supervisor and reducing the resources needed).