The minimum energy potential energy surfaces for combination of NH((3) Sigma(-))+O(P-3) to form HNO((1)A’,(3)A") and N(S-4)+ OH((II)-I-2) to form NOH((3)A"), and the isomerization of HNO((1)A’, (3)A") to NOH((1)A’,(3)A"), decomposition of NOH((1)A’,(3)A") to N(S-4)+OH((II)-I-2) as well as to H(S-2)+NO((II)-I-2) and HNO((3)A") to H(S-2)+NO((II)-I-2) have been obtained by the ab initio methods with geometry optimization at the 6-311G(**)/MP2=full level with corrections for electron correlation at the MP4SDTQ= full level. At all stationary points on the potential energy surfaces (PES), correction for the zero point vibrational energies are made. The addition reactions to form energized adducts have then been analyzed using a bimolecular version of the quantum statistical Rice-Ramsperger-Kassel (QRRK) theory at different temperatures and pressures. Our analysis predicts that at all temperatures isomerization of HNO((3)A") to NOH((3)A") and its reverse isomerization are important. Formation of NO((II)-I-2) in the interstellar clouds can take place from decomposition of NOH((3)A") as well as HNO((3)A").