We present the high resolution ( R \approx 60 000 ) , high signal-to-noise ( S/N \simeq 120 ) spectroscopic analysis of 12 red giant members of the Galactic open cluster NGC 6940 .
We applied Yonsei-Yale isochrones to the colour-magnitude diagram , which suggested an age of 1.1 Gyr for the cluster with a turn-off mass of 2 M _ { \odot } .
Atmospheric parameters ( T _ { eff } , log g , [ Fe/H ] and \xi _ { t } ) were determined via equivalent widths of Fe i , Fe ii , Ti i , and Ti ii lines .
Calculated mean metallicity of the cluster is \langle { [ Fe / H ] } \rangle = 0.04 \pm 0.02 .
We derived abundances of \alpha ( Mg , Si , Ca ) , Fe-group ( Sc , Ti , V , Cr , Mn , Fe , Co , Ni , Cu , Zn ) , and n -capture ( Y , La , Nd , Eu ) elements to be about solar .
Light odd-Z elements Na and Al are slightly enhanced in MMU 108 and MMU 152 by \sim 0.34 dex and \sim 0.16 dex , respectively .
Abundances of light elements Li , C , N , O , and ^ { 12 } C/ ^ { 13 } C ratios were derived from spectrum syntheses of the Li i resonance doublet at 6707 Å , [ O i ] line at 6300 Å , C _ { 2 } Swan bandheads at 5164 Å and 5635 Å , and strong ^ { 12 , 13 } CN system lines in the 7995 - 8040 Å region .
Most carbon isotopic ratios are similar to those found in other solar-metallicity giants , but MMU 152 has an unusual value of ^ { 12 } C/ ^ { 13 } C = 6 .
Evaluation of the LiCNO abundances and ^ { 12 } C/ ^ { 13 } C ratios along with the present theoretical models suggests that all the red giants in our sample are core-helium-burning clump stars .