Application Of Synchrotron Radiation Photoionization Technology In The Study Of Photodissociation And Rydberg States Of Some Small Molecules

In this paper,the absolute absorption spectra and photoionization efficiency spectra of two representative small molecules,nitric oxide(NO)and carbon monoxide(CO),are studied in detail by using synchrotron radiation vacuum ultraviolet photoionization technology.The Rydberg states of NO and CO are studied comprehensively and systematically.And the photodissociation mechanisms of NO and CO have been explored.The absolute absorption spectra of NO and CO are measured by using synchrotron radiation multielectrode photoionization absorption chamber.According to the measured absorption spectra,the Rydberg series of NO and CO are reidentified and ionization energies of their ionic ground states and some excited states are obtained.For NO,the Rydberg series converging to nine electronic states(X~1Σ~+,a~3Σ~+,w~3Δ,b’~3Σ~-,A’~1Σ~-,W~1Δ,b~3Π,A~1Π,and c~3Π)of NO are classified,that are R(X~1Σ~+),R(a~3Σ~+),R(w~3Δ),R(b’~3Σ~-),R(A’~1Σ~-),R(W~1Δ),R(b~3Π),R(A~1Π),and R(c~3Π)series,and the ionization energies of nine electronic states of NO~+are determined;for CO,the Rydberg series converging to X~2Σ~+,(32)~2(47),and B~2Σ~+states of CO(R_X,R_A,and R_B series,respectively)are assigned,and the ionization energies of X~2Σ~+and(32)~2(47)electronic states are determined.The ionization energies of NO and CO are determined to be 9.265 e V and 14.014 e V respectively by means of photoabsorption method.The existed Rydberg series and vibrational progressions have been expanded,and new progressions have been also assigned.The R(X~1Σ~+),R(b’~3Σ~-),R(A’~1Σ~-)and R(W~1Δ)series of NO and the R_X,R_A,and R_B series of CO have been greatly expanded compared with the literatures,and the mean quantum defects of each series also accord with the references.The high-resolution photoionization efficiency spectra of NO and CO have been obtained by synchrotron radiation photoionization mass spectrometry.Combined with quantum chemistry calculations,the photoionization and dissociation processes of NO and CO are studied in detail,and their ionization energies and dissociation limits are determined.Their possible dissociation channels are also explored.Twenty-one dissociation channels of NO and seventeen dissociation channels of CO are identified,some of which are agreement with references.The ionization energies of ground state for NO and CO are determined to be 9.265 e V and 14.015 e V respectively,which are in good accordance with those measured by photoabsorption method in this work.In addition,the R(X~1Σ~+)-ns/ndπseries of NO and the Rydberg series converging to the C~2(50)~+and D~2(47)electronic states of CO are also assigned.The results can provide some references for correlative studies in atmospheric chemistry,astronomy and other fields,as well as the pollution source control.