# Geometric series with polynomial exponent

I came accross this series:

$\sum_{i=p}^{n}{e^{-i(d+i)}}$ with $d \in \mathbb{R}^+$

This looks like a geometric series but it is not. How do I compute its limit when $n \rightarrow +\infty$ ? Which object extends the geometrical series to polynomial exponents?

EDIT: this turns out to be a particular case of this problem which seems to have no general solution yet.