  Multiple ionisation and electron capture are found to be vital mechanisms for
K and L x-ray emissions along with the direct coulomb ionisation in heavy
ion-atom collisions. Naturally, these two mechanisms may also be significant
for M x-ray emissions also. However, these mechanisms associating with the
M-shell are highly complex and not yet studied convincingly. We, in this work,
have discussed about theoretical techniques to study these mechanisms in more
general way, which in turn, almost resolved the wide gap between the theories
and experiments regarding M-shell prevalent in literature up to a good extent.
We have justified this technique with a few representative cases; for example,
the silicon and sulphur projectile ions colliding with the gold and bismuth
targets at beam energies ranging from 5 to 10 MeV. Here, we see that the
capture contribution is much higher than that coming from the multiple
ionisation effect. The combined effects of direct coulomb ionisation associated
with simultaneous multiple ionisation and electron capture give a better
agreement with the measurements up to a good extent.
