Hello! I understand that many of the non-optical methods used to cool down degrees of freedom in a molecule (e.g. buffer gas cooling, supersonic expansion) are able to cool down translational and rotational, but not vibrational motion. Is this because the gap between vibrational levels is much higher, so, for example in a buffer gas, one would need to get rid of all that energy with just one collision, which is highly unlikely? However, mathematically, shouldn't we still expect a Boltzman distribution of vibrational levels, too, regardless of their spacing (i.e. they should thermalize with the buffer gas)? Can someone help me understand this issue (if it is indeed an issue) with vibrational cooling? Thank you!