We present a study of the H i gas content of a large K-band selected sample of 88 close major-merger pairs of galaxies ( H-KPAIR ) which were observed by \it Herschel .
We obtained the 21 cm H i fine-structure emission line data for a total of 70 pairs from this sample , by observing 58 pairs using the Green Bank Telescope ( GBT ) and retrieving the H i data for an addition 12 pairs from the literature .
In this H i sample , 34 pairs are spiral-spiral ( S+S ) pairs , and 36 are spiral-elliptical ( S+E ) .
Based on these data , we studied the H i -to-stellar mass ratio , the H i gas fraction and the H i star formation efficiency ( SFE _ { \mathrm { H { \textsc { i } } } } = star formation rate/ M _ { \mathrm { H { \textsc { i } } } } ) and searched for differences between S+S and S+E pairs , as well as between pairs with and without signs for merger/interaction .
Our results showed that the mean H i -to-stellar mass ratio of spirals in these pairs is = 7.6 \pm 1.0 \% , consistent with the average H i gas fraction of spiral galaxies in general .
The differences in the H i gas fraction between spirals in S+S and in S+E pairs , and between spirals in pairs with and without signs of merger/interaction are insignificant ( < 1 \sigma ) .
On the other hand , the mean SFE _ { \mathrm { H { \textsc { i } } } } of S+S pairs is \sim 4.6 \times higher than that of S+E pairs .
This difference is very significant ( \sim 4 \sigma ) and is the main result of our study .
There is no significant difference in the mean SFE _ { \mathrm { H { \textsc { i } } } } between galaxies with and without signs of merger/interaction .
The mean SFE _ { \mathrm { H { \textsc { i } } } } of the whole pair sample is 10 ^ { -9.55 \pm 0.09 } \mathrm { yr } ^ { -1 } , corresponding to a H i consumption time of 3.5 \pm 0.7 Gyrs .