The Mid-infrared Laser Spectroscopy Of Van Der Waals Complexes Containing Water

IR and microwave spectroscopic studies of molecular complexes have been used to provide detailed information on their structures and intermolecular interactions. Especially, the complexes containing water are very important and have often been treated as prototype systems. The strength of the intermolecular interaction of the binary complexes with water spans a wide range from weak van der Waals to strong hydrogen bonding. This work studies the mid-infrared laser spectroscopy of H2O-CO2and D2O-CO2van der Waals complexes and CO-D2O and N2-D2O complexes. H2O-CO2and D2O-CO2complexes belong to C2v group, while CO-D2O and N2-D2O complexes belong to Cs group. The studies of these spectra will enrich the information of the complexes and help us understand the intermolecular interaction of the complexes better.The rovibrational spectra of H2O-CO2and D2O-CO2complexes have been observed in the V2band region of H2O (D2O) by using the tunable mid-infrared diode laser. The spectra of the H2O-CO2van der Waals complex show an energy level splitting caused by the internal rotation (between the water and carbon dioxide molecules around the van der Waals bond of the complex). The accurate molecular constants and the origins of the first excited state are derived by using the least squares fit with the ground constants fixed at the value of the previous microwave study. The band-origins of H2O-CO2complexes are1595.487664(49) cm-1(even Ka) and1595.480656(47) cm-1(odd Ka), respectively. The band-origins are blue-shifted from the H2O monomer V2band-origion by+0.742684cm-1(even Ka) and+0.735676cm-1(odd Ka), respectivley. The band-origin of the D2O-CO2complex is1178.462876(43) cm-1. Compared with the V2band transition value of D2O monomer, the band-origin is blue-shifted by0.083916cm-1. The inertia defects of the complexes have obtained from the rotation constants. The values of the inertia defects are A/H2o-co2(A1)=0.7069(23) amuA2, A/H2o-co2(B2)=0.9779(23) amuA2and A/D2o-co20.9527(26) amuA2.The spectra of the CO-D2O and N2-D2O complexes in the V2region of D2O monomer have been measured. Three subbands are observed, namely Ka:0<←0(a-type), Ka:0←1(4-type) and Ka:1<←0(b-type). The spectra show that each rovibrational state is splitted into two tunneling state (A state and B state) due to the tunneling motion between the two equivalent hydrogen-bonded configurations. The band-origins of the first excited state of CO-D2O complex are1180.62418(18) cm-1(A state) and1180.61457(17) cm-1(B state). Compared with the V2band transition value of D2O monomer, they are blue-shifted by2.1613cm’1(A state) and2.15169cm-1(B state), respectively. The origins of N2-D2O complex are1179.64427(20) cm-1(A state) and1179.60669(19) cm-1(B state), respectively. They are blue-shifted by1.18139cm-1(A state) and1.14381cm-1(B state), respectively. Not only the inertia defects and the intermolecular distances of the complexes but also the tunneling splitting have been obtained from the rotational constants. The inertia defects of A state and B state of the ground state of the CO-D2O complex are0.673(21) amu*A and0.564(25) amu*A, respectively. And the inertia defects of the excited state are0.673(21) amu*A (A state) and0.564(25) amu*A (B state). The intermolecular distances of the excited state of the CO-D2O complex are3.9415A (A state) and3.9406A (B state). The inertia defects and the intermolecular distances of A state and B state of the ground and excited state of the N2-D2O complex are AIG(A)=1.047(38) amuA2, AIG(B)=0.545(43) amuA2, AIE(A)=1.208(36) amuA2, AIE(B)=0.717(37) amuA2, RG(A)=3.8309A, RG(B)=3.8295A, RE(A)=3.8274A, and RE(B)=3.8259A. There are two methods for calculating the tunneling splitting, either by using the effective rotational constant A or the band-origins of the complexes. The tunneling splitting of the CO-D2O and N2-D2O complexes calculated with band-origins are0.02523(37) and0.12562(74) cm-1, respectively. Compared with the results by using the effective rotational constant A, the tunneling splitting is reduced by2.6%for CO-D2O) and2.2%for N2-D2O, respectively.