Near-Infrared Electronic Transitions of Pb(2).

Emission spectra of two new electronic transitions of Pb(2) have been measured with a Fourier transform spectrometer in the 5200-8500 cm(-1) range. The emissions were observed from the afterglow of a microwave discharge in a mixture of Pb(x) vapor with hydrogen and argon carrier gas. By comparison with the results of ab initio calculations, the spectra are assigned to transitions from the lowest 1(g) and 1(u) states to the X(1)0(+)(g) ground state. The X(2)1(g) --> X(1)0(+)(g) transition between the fine-structure components of the X(3)Sigma(-)(g) ground state must be magnetic dipole in nature and thus is the first purely magnetic dipole fine-structure transition observed in the optical region. The 1(u) state is mostly a component of the low-lying inverted A(3)Pi(u) state and so is denoted A(2)1(u). Vibrational analyses have yielded the following electronic energies and vibrational constants for (208)Pb(2) (in cm(-1)): X(1)0(+)(g): omega(e) = 110.20(2), omega(e)x(e) = 0.341(2); X(2)1(g): T(e) = 5304.9(1), omega(e) = 120.57(7), omega(e)x(e) = 0.254(14); A(2)1(u): T(e) = 7817.5(2), omega(e) = 126.45(6), omega(e)x(e) = 0.399(11), where the numbers in parentheses are the standard deviations of the parameters. Copyright 2000 Academic Press.

Experimental and Theoretical Study of the Electronic States and Spectra of BiNa.

Gas-phase emission spectra of the hitherto unknown free radical BiNa have been measured in the NIR range with a Fourier transform spectrometer. The emissions were observed from a fast-flow system in which bismuth vapor in argon carrier gas was passed through a microwave discharge and mixed with sodium vapor in an observation tube. Two systems of blue-degraded bands observed in the ranges 8900-9800 and 7200-7800 cm(-1) were measured at high spectral resolution and vibrational and rotational analyses were performed. To aid in the analysis of the experimental data, a series of relativistic configuration interaction calculations has been carried out to obtain potential curves for the low-lying states of BiNa and also electric dipole transition moments connecting them. As in the isovalent BiH system, the ground state of BiNa is found to be X(3)Sigma(-) with a spin splitting of about 1769 cm(-1). The first excited state is A(3)Pi, and the observed band systems are assigned to the transitions A(3)Pi(A(2)0(+)) --> X(3)Sigma(-)(X(1)0(+), X(2)1). Comparison with earlier work on the isovalent BiH system emphasizes that the relative weakness of the varsigma MO in BiNa is responsible for qualitative differences in the electronic spectra of these two systems. Copyright 2000 Academic Press.

High-Resolution Fourier-Transform Study of the b(1)Sigma(+) --> X(3)Sigma(-) and a(1)Delta --> X(3)Sigma(-) Transitions of SO.

Emission spectra of the b(1)Sigma(+) --> X(3)Sigma(-) and a(1)Delta --> X(3)Sigma(-) transitions of SO in the near-infrared spectral region were studied at high spectral resolution with a Fourier-transform spectrometer. The 0-0 band of the b --> X system was measured at high signal/noise and four magnetic dipole branches were observed in addition to the previously known five electric dipole branches. From the relative line intensities and the radiative lifetime of the b state, the electric and magnetic transition moments were determined to be µ(0) = +/-0.0042 ea(0), µ(1) = -/+0.0047 ea(0), and M = 0.16 µ(B). All nine electric dipole branches were observed in the 0-0 band of the a --> X transition. Fixing the rotational constants of the X(3)Sigma(-) ground state to microwave values, the following parameters were obtained for the a(1)Delta state (in cm(-1)): v(00) = 5862.1853(1), B(0) = 0.71033746(37), D(0) = 1.16814(46) x 10(-6) (with H(0) fixed to -3.99 x 10(-13)), where the numbers in parentheses are the standard deviations of the parameters. Copyright 1999 Academic Press.

The b1Sigma+(b0(+)) --> X3Sigma-(X10(+), X21) and a1Delta(a2) --> X21 Transitions of AsI.

Emission spectra of the b1Sigma+(b0(+)) --> X3Sigma-(X10(+), X21) and a1Delta(a2) --> X21 transitions of AsI have been measured in the near-infrared spectral region with a Fourier-transform spectrometer. The arsenic iodide radicals were generated and excited in a fast-flow system by reaction of arsenic vapor (Asx) with iodine and microwave-discharged oxygen. The most prominent features in the spectrum are six band sequences of the strong b1Sigma+(b0(+)) --> X3Sigma-(X10(+)) transition in the range 800-900 nm. With much lower intensities the hitherto unknown b1Sigma+(b0(+)) --> X3Sigma-(X21) subsystem and the a1Delta(a2) --> X21 transition near 1660 nm are observed. Vibrational analyses have yielded improved molecular constants for the X10(+) and b0(+) states and first values of the electronic energies and vibrational constants of the X21 and a2 states (in cm-1), X21: Te = 289.8(2), omegae = 255.2(2), omegaexe = 0.68(7), a2: Te = 6305.4(3), omegae = 267.8(1), omegaexe = 0.56(2), where the numbers in parentheses are the standard deviations of the parameters. Copyright 1999 Academic Press.

The b1Sigma+(b0(+)) --> X3Sigma-(X10(+), X21) and a1Delta(a2) --> X21 Transitions of SbF, SbCl, SbBr, and SbI.

Emission spectra of the a1Delta(a2) --> X21 and b1Sigma+(b0(+)) --> X3Sigma-(X10(+), X21) transitions of SbF, SbCl, SbBr, and SbI have been observed in the near-infrared spectral region. The antimony halide radicals were generated and excited in a fast-flow system by reaction of antimony vapor (Sbx) with the halides and microwave-discharged oxygen. The NIR chemiluminescence was measured with a Fourier-transform spectrometer equipped with Ge and InSb detectors. The spectra contain the known b1Sigma+(b0(+)) --> X3Sigma-(X10(+), X21) transitions in the range 730-910 nm and the hitherto unknown a1Delta(a2) --> X21 transitions in the range 1600-1900 nm. Vibrational analyses have yielded improved molecular constants for the X10(+), X21, and b0(+) states and the following constants of the a2 states (in cm-1): 121SbF: Te = 6815.6(5), omegae = 615.75(3), omegaexe = 2.62(1); 121Sb35Cl: Te = 6546.3(2), omegae = 379.8(1), omegaexe = 1.20(2); 121Sb79Br: Te = 6496.4(4), omegae = 265.9(2), omegaexe = 0.55(3); 121SbI: Te = 6366.7(3), omegae = 214.20(5), omegaexe = 0.430(9), where the numbers in parentheses are the standard deviations of the parameters. Copyright 1999 Academic Press.

LIF Studies of the Ã1A' States of BiOH and BiOD.

Electronic spectra of the recently discovered BiOH and BiOD radicals have been studied by means of laser-induced fluorescence measurements in the 400-1000 nm range. Laser excitation spectra observed in the range 430-450 nm are attributed to transitions from the &Xtilde;1A' ground state to the theoretically predicted Ã1A' state. Fluorescence spectra from the Ã1A',nu'3 = 0, 1 levels consist of short nu"3 progressions to the lower states &Xtilde;1A', &Xtilde;3A', and ã1A'. Laser excitation spectra in the range 580-620 nm contain bands with both DeltaKa = 0 and DeltaKa = +/-1 subbands. They are attributed to hybrid bands of the Ã1A' <-- &Xtilde;3A' transition. Analyses of the spectra have yielded vibronic energy levels of the &Xtilde;1A', &Xtilde;3A', ã1A', and Ã1A' states of both isotopes and effective rotational constants A - 1/2(B + C) and DK for some levels. The radiative lifetime of the Ã1A',000 state was found to be 0.92 +/- 0.03 µs. Copyright 1998 Academic Press.

Gas Phase LIF Study of the b1Sigma+(b0(+)) left and right arrow X3Sigma-(X10(+), X21) Transition of NI.

First gas phase spectra of the nitrogen monoiodide radical NI are reported. The b1Sigma+(b0(+)) left and right arrow X3Sigma-(X10(+), X21) transition of NI has been studied by laser-induced fluorescence measurements. Ground state NI radicals were generated in a fast-flow system by reaction of microwave-discharged nitrogen with iodine vapor. Vibrational levels v = 0, 1, and 2 of the b1Sigma+ state were excited with a pulsed dye laser. Rotational and vibrational constants of the X3Sigma- and b1Sigma+ states were deduced from analysis of high-resolution excitation spectra. Time-resolved measurements of the fluorescence decay and measurements of relative line and band intensities allowed determination of the radiative lifetime of the b state, of band transition probabilities, and of the ratio of transition moments µ0/µ1 for the b0(+) --> X10(+) and b0(+) --> X21 subtransitions. Comparison of calculated and experimental line intensities and FC factors shows that treatment of the X3Sigma- state in terms of a Hund's case (a) formalism is preferable to use of a case (c) formalism. Copyright 1998 Academic Press.

Electronic States and Spectra of BiO.

The electronic spectrum of the BiO radical has been studied by Fourier transform emission spectroscopy, laser-induced fluorescence, and excimer laser photolysis techniques. Six new electronic states, A1 (Omega = 3/2) (Te = 11 528.8 cm-1, omegae = 530.4 cm-1, omegaexe = 2.42 cm-1), G (Omega = 3/2) (Te = 20 273 cm-1, omegae = 499 cm-1, omegaexe = 2.6 cm-1), H (Omega = 1/2) (Te = 20 469.76(6) cm-1, omegae = 471.63(18) cm-1, omegaexe = 2.153(35) cm-1), I (Omega = 1/2) (Te = 21 982.50(2) cm-1, omegae = 506.50(11) cm-1, omegaexe = 3.263(34) cm-1), J (Omega = 3/2) (Te = 25 598.95(42) cm-1, omegae = 489.95(16) cm-1, omegaexe = 2.309(45) cm-1), and K (Omega = 1/2) (Te = 26 744.7(2) cm-1, omegae = 420.6(4) cm-1, omegaexe = 5.25(5) cm-1), and 14 new electronic transitions (A1 <-- X1, G --> X2, H left and right arrow X1, H --> A2(A), I left and right arrow X1, I --> A2, J left and right arrow X1, J left and right arrow X2, K left and right arrow X1, K left and right arrow X2, K --> A2, B left and right arrow X2, B --> A2, C left and right arrow X2) have been detected. Time-resolved measurements of the fluorescence decays have yielded the radiative lifetimes of the v = 0 levels of most states up to <30 500 cm-1 energy (tauX2 = 480 +/- 100 µs, tauA2 = 9.3 +/- 1.5 µs, tauH = 15 +/- 3 µs, tauI = 16 +/- 3 µs, tauJ = 4.9 +/- 0.9 µs, tauK = 2.6 +/- 0.3 µs, tauB = 0.55 +/- 0.08 µs, tauC = 0.84 +/- 0.15 µs) and rate constants for quenching of the states by some rare gas atoms and simple molecules. The new electronic states A1, G, H, I, J, and K and the previously known levels X1, X2, A2(A), B, C, and D are assigned to spin-orbit states arising from low-energy valence configurations of BiO with the help of detailed theoretical data calculated by Alekseyev et al. (J. Chem. Phys. 100, 8956-8968 (1994)). Copyright 1998 Academic Press.

High-Resolution Study of the X22Pi3/2 --> X12Pi1/2 Fine Structure Transitions of PbF and PbCl.

The near-infrared emission spectra of the X22Pi3/2 --> X12Pi1/2 fine structure transitions of PbF and PbCl have been investigated by high-resolution Fourier-transform spectrometry. Despite the large fine structure splitting, the bands can be equally well analyzed with Hund's case (a) or case (c) formalisms. Accurate rotational constants for the v = 0 vibrational levels of 208PbF and 208Pb35Cl and hyperfine structure constants for 207PbF have been derived. Copyright 1998 Academic Press.

LIF Study of the b1Sigma+(b0(+)) left and right arrow X3Sigma-(X10(+),X21) Transitions of SbH and SbD.

The b1Sigma+(b0(+)) left and right arrow X3Sigma-(X10(+),X21) transitions of SbH and SbD have been studied by laser-induced fluorescence measurements. Ground state SbH(SbD) radicals were generated in a fast-flow system by reaction of microwave-discharged hydrogen (deuterium) with antimony vapor. Vibrational levels v = 0 and 1 of the b1Sigma+ state were excited with a pulsed dye laser. In addition to five electric dipole branches SR, QP, QR, QQ, and OP, weak magnetic dipole branches PQ were observed in the 0-0 bands of the b1Sigma+ <-- X3Sigma- transitions. Rotational and vibrational constants of the X3Sigma- and b1Sigma+ states were deduced from high-resolution excitation spectra. Time-resolved measurements of the fluorescence decay and measurements of relative line and band intensities allowed determination of the radiative lifetime of the b1Sigma+ state of SbH (tau = 173 +/- 3 µs) and of the electric and magnetic dipole transition moments µ0 = +/-0.036 D, µ1 = -/+0.058 D, |M| = 1.62 Bohr magnetons. Copyright 1998 Academic Press.

High-Resolution Study of the A2A' --> X2A" Transition of HO2: Analysis of the 000-000 Band

The near-infrared emission spectrum of the A2A' --> X2A" transition of the hydroperoxyl radical, HO2, has been studied by Fourier transform spectrometry. The 000 --> 000 band has been recorded at high spectral resolution. DeltaKa = +/-1 subbands up to Ka' = 9 --> Ka" = 8 and Ka' = 8 --> Ka" = 9 comprising lines from rotational levels up to N' = 32 have been observed. With about a factor of 10 lower intensity, DeltaKa = 0 subbands 0-0 to 6-6 were found which are shown to be due to magnetic dipole transitions. In addition, in the 2-2 sub-band "forbidden" electric dipole lines were observed. These likely are induced by Renner-Teller interaction. Local perturbations extending over 3-10 N' values are found in the Ka' = 0-7 levels of the A2A' state. One series of perturbations is attributed to DeltaKa = 0, DeltaJ = 0 interactions with the 112 level of the X2A" ground state. Copyright 1997 Academic Press. Copyright 1997Academic Press