The rovibrational transition of 1H 35Cl with v = 0 to 1, J = 11 to 10 occurs at 2757.89 cm-1 , and the transition with v = 0 to 1, J = 10 to 9 occurs at 2779.07 cm-1 . From this information, i) calculate the spring constant of the vibrational potential (assuming the harmonic approximation and rigid rotor approximation) and ii) the equilibrium length of the HCl bond.