  We present a study of the molecular gas in early-mid stage major-mergers,
with a sample of 43 major-merger galaxy pairs selected from the Mapping Nearby
Galaxies at Apache Point Observatory (MaNGA) survey and a control sample of 195
isolated galaxies selected from the xCOLD GASS survey. Adopting kinematic
asymmetry as a new effective indicator to describe the merger stage, we aim to
study the role of molecular gas in the merger-induced star formation
enhancement along the merger sequence of galaxy pairs. We obtain the molecular
gas properties from CO observations with the James Clerk Maxwell Telescope
(JCMT), Institut de Radioastronomie Milimetrique (IRAM) 30-m telescope, and the
MASCOT survey. Using these data, we investigate the differences in molecular
gas fraction ($f_{\rm H_{2}}$), star formation rate (SFR), star formation
efficiency (SFE), molecular-to-atomic gas ratio ($M_{\rm H_{2}}/M_{\rm HI}$),
total gas fraction ($f_{\rm gas}$), and the star formation efficiency of total
gas (${\rm SFE_{gas}}$) between the pair and control samples. In the full pair
sample, our results suggest the $f_{\rm H_{2}}$ of paired galaxies is
significantly enhanced, while the SFE is comparable to that of isolated
galaxies. We detect significantly increased $f_{\rm H_{2}}$ and $M_{\rm
H_{2}}/M_{\rm HI}$ in paired galaxies at the pericenter stage, indicating an
accelerated transition from atomic gas to molecular gas due to interactions.
Our results indicate that the elevation of $f_{\rm H_{2}}$ plays a major role
in the enhancement of global SFR in paired galaxies at the pericenter stage,
while the contribution of enhanced SFE in specific regions requires further
explorations through spatially resolved observations of a larger sample
spanning a wide range of merger stages.
