The vacuum ultraviolet (VUV) pulsed field ionization−photoelectron (PFI−PE) spectrum for trans-dichloroethene (trans-ClCHCHCl) has been measured in the energy range 77 600−79 200 cm-1. On the basis of the spectral simulation of the origin VUV−PFI−PE vibrational band, we have determined the IE(trans-ClCHCHCl) to be 77 678.4 ± 2.0 cm-1 (9.630 97 ± 0.000 25 eV). The vibrational bands resolved in the VUV−PFI−PE spectrum of trans-ClCHCHCl are assigned on the basis of ab initio vibrational frequencies and calculated Franck−Condon factors for the ionization transitions, yielding eight vibrational frequencies ν1 + = 163 cm-1, ν3 + = 367 cm-1, ν4 + = 871 cm-1, ν5 + = 915 cm-1, ν6 + = 944 cm-1, ν8 + = 1235 cm-1, ν9 + = 1258 cm-1, ν10 + = 1452 cm-1. The distinct feature of the VUV−PFI−PE spectrum is the strong vibrational progression of the ν3 + (CCl stretching) mode of trans-ClCHCHCl+, which is consistent with the theoretical geometry calculation, predicting a significant change in the CCl bond distance upon photoionization of trans-ClCHCHCl. We have also determined the frequency (3068 cm-1) for the ν11 + (CH stretching) vibrational mode of trans-ClCHCHCl+ by employing the VUV−IR-photoinduced Rydberg ionization (VUV−IR−PIRI) method. The VUV−IR−PIRI spectra for trans-ClCHCHCl prepared in the effective principal quantum numbers, n* = 14 and 36, are found to be identical, supporting the previous conclusion that the Rydberg electron behaves as a spectator; i.e., the Rydberg electron orbital is conserved during the IR excitation of the ion core.

The preparation of methyl iodide (CH(3)I) in selected rovibrational states [nu(7)=1 (C-H stretch); J] by infrared (IR) excitation prior to vacuum ultraviolet (VUV) photoionization has greatly simplified the observed pulsed field ionization-photoelectron (PFI-PE) spectra, allowing the direct determination of the rotational constants B(+)(C(+))=0.254+/-0.003 cm(-1) for CH(3)I(+)(X (2)E(3/2);nu(7) (+)) and the ionization energy (76 896.9+/-0.2 cm(-1)) for CH(3)I(+)(X (2)E(3/2);nu(7) (+)=1,J(+)=3/2)<--CH(3)I(X (1)A(1);nu(7)=1,J=0). The IR-VUV-PFI-PE and IR-VUV-photoion measurements also provide relative state-to-state (nu(7) (+)=1, J(+)<--nu(7)=1, J) cross sections for the photoionization process.

The vacuum ultraviolet (VUV) laser pulsed field ionization photoelectron (PFI-PE) spectrum of cis-dichloroethene (cis-ClCH[Double Bond]CHCl) has been measured in the energy region of 77 600-79 500 cm(-1). On the basis of the semiempirical simulation of the origin PFI-PE band, we have obtained the IE(cis-ClCH[Double Bond]CHCl) to be 77 899.5+/-2.0 cm(-1) (9.658 39+/-0.000 25 eV). The assignment of the vibrational bands resolved in the VUV-PFI-PE spectrum are guided by high-level ab initio calculations of the vibrational frequencies for cis-ClCH[Double Bond]CHCl(+) and the Franck-Condon factors for the ionization transitions. Combining the results of the present VUV-PFI-PE measurement and the recent VUV-infrared-photoinduced Rydberg ionization study, the vibrational frequencies for eleven of the twelve vibrational modes of cis-ClCH[Double Bond]CHCl(+) have been experimentally determined: nu(1) (+)(a(1))=181 cm(-1), nu(2) (+)(a(2))=277 cm(-1), nu(3) (+)(b(2))=580 cm(-1), nu(4) (+)(b(1))=730 cm(-1), nu(5) (+)(a(1))=810 cm(-1), nu(6) (+)(a(2))=901 cm(-1), nu(8) (+)(a(1))=1196 cm(-1), nu(9) (+)(b(2))=1348 cm(-1), nu(10) (+)(a(1))=1429 cm(-1), nu(11) (+)(b(2))=3067 cm(-1), and nu(12) (+)(a(1))=3090 cm(-1)). These values are compared to theoretical anharmonic vibrational frequencies obtained at the MP2/6-311G(2df,p) and CCSD(T)/6-311G(2df,p) levels. The IE prediction for cis-ClCH[Double Bond]CHCl has also been calculated with the wave function based CCSD(T)/CBS method, which involves the approximation to the complete basis set (CBS) and the high-level correlation corrections. The theoretical IE(cis-ClCH[Double Bond]CHCl)=9.668 eV thus obtained is found to have a deviation of less than 10 meV with respect to the experimental IE value.

By preparing methyl bromide (CH3Br) in selected rotational levels of the CH3Br(X(1)A1; v1 = 1) state with infrared (IR) laser excitation prior to vacuum-ultraviolet (VUV) laser pulsed field ionization-photoelectron (PFI-PE) measurements, we have observed rotationally resolved photoionization transitions to the CH3Br(+)(X(2)E(3/2); v1(+) = 1) state, where v1 and v1(+) are the symmetric C-H stretching vibrational mode for the neutral and cation, respectively. The VUV-PFI-PE origin band for CH3Br(+)(X(2)E(3/2)) has also been measured. The simulation of these IR-VUV-PFI-PE and VUV-PFI-PE spectra have allowed the determination of the v1(+) vibrational frequency (2901.8 +/- 0.5 cm(-1)) and the ionization energies of the origin band (85 028.3 +/- 0.5 cm(-1)) and the v1(+) = 1 <-- v1 = 1 band (84 957.9 +/- 0.5 cm(-1)).

Public reoortiiKi buitien for this collection of information is estimated to average 1 hour per response, including the lime for reviewing instructois, searching easting data sounces galhenng and rnaintaimg the Sl^^,^S^^nd <^c*Snq and reviewing this collection of informatfon. Send comments regarding this burden estimate or any other aspect of this collecbon of information, ineludKig suggestions for reducing ^.^^to^^^^^^^/^alNngt^Headquarteis Services, Directorate for Infomiation . 1215 Jeffeison Davis H^hv^y, Surte 12M, Arlington, VA 22202-^R^^S^d bea«lre that notvSthstandind any other provision of law, no person shall be subject to any penalty for foiling to comply with a coHecbon of infomnaton if it does not display a cunently SM OMR^Mitroi nirober. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) AFRL-VS-HA-TR-2004-1100 SPONSOR/MONITOR'S ACRONYM(S)AFRL/VSBXT SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION / AVAILABILITY STATEMENT ABSTRACTWe have developed an octopole-quadrapole photoionization apparatus at the Advanced Light Source for absolute integral cross-section measurements of rovibrational-state-selected ion-molecule reactions. This apparatus consists of a high-resolution photoionization ion source, a wired ion gate lens, a dual radio-frequency (rO octopole ion guide reaction gas cell, and a quadmpole mass spectrometer for reactant and product ion detection. The unique feature of this apparatus is the implementation of the high-resolution pulsed field ionization-photoelectron (PFI-PE)-photoion coincidence (PFI-PEPICO) technique, which has allowed the rotational-state selection of diatomic ions for ion-molecule reaction studies, The novel application of the wired ion gate lens for the rejection of false coincidence background ions is described. This application, along with the difFerenti?d-ion-gate scheme, has made possible the measurements of rovibrationai-state-selected absolute integral reaction cross sections for ion-molecule collisions using the PFI-PE-secondaiy ion coincidence (PFI-PESICO) method. ' We have developed an octopole-quadrupole photoionization apparatus at the Advanced Light Source for absolute integral cross-section measurements of rovibrational-state-selected ion-molecule reactions. This apparatus consists of a high-resolution photoionization ion source, a wired ion gate lens, a dual radio-frequency (rf) octopole ion guide reaction gas cell, and a quadrupole mass spectrometer for reactant and product ion detection. The unique feature of this apparatus is the implementation of the high-resolution pulsed field ionization-photoelectron (PFI-PE)-photoion coincidence (PFI-PEPICO) technique, which has allowed the rotational-state selection of diatomic ions for ion-molecule reaction studies. The novel application of the wired ion gate lens for the rejection of false coincidence background ions is described. This application, along with the diflferential-ion-gate scheme, has made possible the measurements of rovibrational-state-selected absolute integral reacti...