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The v2 = 1←0, 2←1, and 3←2 bands of the methyl radical were observed in the gas phase by infrared tunable diode laser spectroscopy at 606.4531, 681.6369, and 731.0757 cm−1. The observed vibration–rotation spectra were analyzed to derive precise values for the rotational constants, centrifugal distortion constants, and spin–rotation interaction constants. The absence of N = odd, K = 0 levels in the v2 = even states and of N = even, K = 0 levels in the v2 = odd states was confirmed, indicating that each vibrational state is nondegenerate. The observed band origins, when analyzed, led to a potential function for the out‐of‐plane bending vibration that has no potential hump at the planar configuration. The large negative anharmonicity of this potential was ascribed to a vibronic interaction with excited electronic states. The methyl radical was generated by a 60 Hz discharge in di‐tert‐butyl peroxide and was found to have a lifetime of about 1.4 msec; its concentration in the absorption cell was estimated to ...

The high-resolution infrared diode laser spectrum of the ν 2 band of 15 N 16 O 2 was observed in the region 670 to 780 cm −1 . The band center was determined to be 739.9505(6) cm −1 . A set of molecular constants was derived which reproduces the vibration-rotation energies of the ν 2 state within the error of 0.003 cm −1 in the range of K up to 5 and N up to 40.

The 2P1/2–2P3/2 fine structure transitions in the ground (np5) state of the neon (n=2) and argon (n=3) atomic ions have been observed in absorption in the positive column of a liquid–nitrogen cooled discharge cell, by employing tunable infrared diode lasers as sources. The transition frequencies were measured to be 780.4240±0.0011 and 1431.5831±0.0007 cm−1 for Ne+ and Ar+, respectively. A few transitions have also been observed for the neutral Ne and Ar atoms.

The ν1 band of the CCO radical in the X 3Σ− ground electronic state has been observed in the gas phase by diode laser kinetic spectroscopy. The CCO radical was generated by the 193 or 248 nm excimer laser photolysis of carbon suboxide. By fixing ground state parameters to the microwave values, the band origin and the vibrational changes of the rotational (αB=B0−B1) and spin–spin interaction (αλ=λ1−λ0) constants have been determined to be 1970.864 34(95), 0.003 075 4(85), and 0.008 3(12) in cm−1 with 2.5 standard errors in parentheses.

The ν3 fundamental band of the CH3 radical has been detected in absorption with a tunable difference frequency laser. Zeeman modulation is found to be inefficient, because the spin‐rotation interaction is small. The molecular constants in the ν3 vibrational state have been determined with the molecular constants in the ground state fixed at the values determined from the analysis of the ν2 band. The main parameters thus obtained are the band origin ν0=3160.8212(12), B3=9.471 10(14), C3=4.701 67(15), (Cζ)3=0.345 88 (22), and q3=0.006 42(25), all in cm−1 with one standard deviation in parentheses. The transition frequencies and the molecular constants of the ν3 band may be useful in a search for interstellar CH3.

The reaction of O(1D)+SiH4 was studied by means of infrared diode laser kinetic spectroscopy, where O(1D) was prepared by ArF excimer laser irradiation of N2O. Vibrationally ground state silyl radicals and v=2 OH radicals were identified, and their time profiles were discussed on the basis of an appropriate reaction mechanism.

The ν2 band of the silylene SiH2 molecule in X 1 A1 was observed for the first time in the gas phase by using infrared diode laser kinetic spectroscopy. Silylene molecules were generated by the photolysis of phenylsilane at 193 nm. The observed spectrum was analyzed to determine the rotational and centrifugal distortion constants in the ground and v2 =1 states and the band origin ν0 =998.6241(3) cm−1 with one standard deviation in parentheses. The significance of the derived parameters is discussed in detail.

The vibration-rotation spectra of the SF radical were observed by an infrared diode laser spectrometer. The SF radical was generated directly in a cell by glow discharge in a mixture of carbonyl sulfide and carbon tetrafluoride. Zeeman modulation and discharge current modulation were employed to discriminate SF lines from many lines of the reactants and other products. Thirty two lines were assigned to the v = 1 ← 0 and 2 ← 1 bands of both 2 Π 1 2 and 2 Π 3 2 spin states. A least-squares analysis of all the assigned lines provided precise values for molecular parameters in v = 1 and 2 and the two band origins, where ground-state constants were constrained to microwave results. The harmonic frequency ω e was thus determined to be 837.6418(13) cm −1 , and the equilibrium bond length r e was calculated from the B e rotational constant to be 1.596 244(22) A with the error in parentheses, which included 2.5 standard deviations and the uncertainty of Planck's constant.

The fundamental band of the SCl radical in the 17.4-μm region was investigated by using a Zeeman-modulated tunable diode laser spectrometer equipped with a multiple-reflection absorption cell, and 27 transitions in the X 2 Π 3 2 state were observed and measured, while no spectral lines were identified in the 2 Π 1 2 state. An analysis of the observed spectrum gave the following molecular constants (in cm−1) with three standard deviations in parentheses; ν0 = 574.612 70(81), B″ = 0.257 907(45), B′ = 0.256 345(42), D″ = 0.229(48) × 10−6, and D′ = 0.226(42) × 10−6.

The v = 1 ← 0 vibration-rotation bands of 12 C 32 S, 12 C 34 S, 12 C 33 S, and 13 C 32 S were measured by using a tunable diode laser. The v = 2 ← 1 hot band of 12 C 32 S was also observed. From the band origins which were obtained by the analysis of the observed spectra the harmonic frequency ω e and the anharmonicity constant ω e x e were calculated to be 1285.1392(40) cm −1 and 6.4864(20) cm −1 , respectively, with the standard errors in parentheses.

The fundamental band of the FO radical in the 9.6-μm region was studied using a tunable diode laser and a Zeeman-modulated multiple-traversal absorption cell. Although it was not possible to detect any transitions belonging to the 2 Π 1 2 substate, 14 transitions of 2 Π 3 2 were observed and accurately measured. Analysis of these measurements gave the following molecular parameters (with A0 = A1 fixed at −177.3 cm−1): ν0 = 1033.4829(5) cm−1, B0 = 1.05285(9) cm−1, B1 = 1.03933(8) cm−1, D0 = 4.4(4) × 10−6 cm−1, and D1 = 4.4(3) × 10−6 cm−1.

The ν 2 fundamental band ( ν 0 = 1497.3 cm −1 ) of the NH 2 radical was studied by CO laser magnetic resonance. The NH 2 radicals were produced by the reaction of hydrated hydrazine and hydrogen atoms obtained from a discharge in water vapor. The assignment was established for about 160 Zeeman resonances which involved levels with 0 ≦ N ≦ 7 and 0 ≦ K a ≦ 5. From an analysis of the observed spectra, combined with the previously reported 10 μm and far infrared LMR spectra, the band origin, the rotational, the centrifugal distortion, and the spin-rotation constants were accurately determined both for the ν 2 = 1 and the ground states. As in the case of HCO, large changes of A , Δ K , ϵ aa , and Δ K s were observed upon the excitation of the ν 2 mode.

In the course of measurements of a discharge current in a CO2 laser tube, current oscillations of about 20 kHz were observed just after a Q-switched laser pulse emission. The current oscillations were also found, when the Q-switched laser pulse was incident on discharged plasmas of CO2 or N2. The observed frequencies were 9 kHz in CO2 plasma and 13 kHz in N2 plasma, when a discharge tube of inner diameter of 43 mm was used. Theoretical analysis shows that an acoustic wave excited by the laser pulse gives rise to the current oscillation which we observed.

The infrared absorption spectrum of the PF radical in the X 3Σ− ground electronic state has been observed using a Zeeman modulated diode laser spectrometer. The radical was produced in a multiple‐reflection absorption cell by a dc glow discharge in a mixture of PH3 and CF4. The F1 and F3 spin components of five vibration–rotation transitions of the v=1–0 band have been recorded in the region of 823 to 830 cm−1. By constraining molecular constants of the v=0 state to the values previously determined by microwave spectroscopy, the band origin, the vibration–rotation constant αB=B0−B1, and the vibrational change of the spin–spin interaction constant αλ=λ1−λ0 have been determined from the observed spectrum to be 837.816 36(70), 0.004 639 4(70), and −0.005 04(91) in cm−1, respectively, with one standard deviation in parentheses. The sign of αλ is the same as those of NCl and PCl, but is opposite to those of O2, SO, S2, and SeO.

Four vibration–rotation transitions of 32S16O in the 1Δ state were observed by laser magnetic resonance spectroscopy with a C18O2 laser in the 9 μm region as a source. Additional measurements were also made on two transitions of 34S16O. The band origin, the rotational constant, and the g factor in the v=1 state were determined by fixing the molecular constants in the ground vibrational state to those obtained either from microwave spectra or from reanalyzed electron paramagnetic resonance spectra. The second‐order effect on the molecular g factor was discussed. The equilibrium bond length was determined to be 1.48886±0.00026 A. The harmonic frequency and the vibrational anharmonicity constant were calculated from the band origins of the two isotopic species to be ωe=1115.349±0.081 cm−1 and ωexe=6.978±0.041 cm−1, respectively. The errors are all 2.5 times the standard deviations.

The silyl radical Si${\mathrm{H}}_{3}$ has been detected in a silane-discharge plasma through the observation of the ${\ensuremath{\nu}}_{2}$ band by infrared diode-laser spectroscopy. The band was observed to consist of two inversion-doubling components, ${1}^{\ensuremath{-}}$ \ensuremath{\leftarrow} ${0}^{+}$ and ${1}^{+}$ \ensuremath{\leftarrow} ${0}^{\ensuremath{-}}$, and the analysis of the observed spectrum yielded molecular constants in the ${\ensuremath{\nu}}_{2}=0 \mathrm{and} 1$ states. The barrier height to the inversion has been calculated from the observed band origins to be 1868 ${\mathrm{cm}}^{\ensuremath{-}1}$. The same analysis yielded the height of the pyramid to be 0.465 \AA{}, which was combined with the observed constant ${B}_{0}$ to calculate $r(\mathrm{SiH})=1.468$ \AA{} and $\ensuremath{\theta}(\mathrm{HSiH})=110.5\ifmmode^\circ\else\textdegree\fi{}$.

Generation of the CCCO molecule was observed through its microwave spectrum in a dc glow discharge of carbon suboxide. Thirteen rotational transitions J = 7-6 to 19-18 were measured in the frequency region 67–183 GHz with the use of a source-modulation microwave spectrometer. A least-squares analysis of 19 observed spectral lines, including the six previously reported by Brown et al., yielded the following revised molecular constants for CCCO: B o = 4810.88624(65) MHz and D o = 0.00077707(130) MHz, with 3σ in parentheses. The concentrations of CCO as well as CCCO produced in the glow discharge are estimated to be about 11 ppm.

By using a tunable diode laser, the decay of the absorption intensity with time, after the discharge generating the radical was switched off, was measured for a line [Q4(4)] of the CH3 ν2 fundamental band. When combined with a literature value of the CH3 recombination rate constant, the present result gave an estimate for the steady‐state concentration of the CH3 radical. The steady‐state absorbance of the Q4(4) line was also measured, and the two results were used to calculate the transition moment of the CH3 v2=1←0 band to be 0.280±0.049 D.

The ν1 (C–D stretch) fundamental band of the DCO+ molecular ion has been studied using a tunable diode laser spectrometer and a liquid‐nitrogen‐cooled hollow‐cathode absorption cell with magnetic field modulation. A total of eight lines were measured, and their analysis yielded the ν1 band origin, 2584.5618(14) cm−1, and the change in rotational constant, α1=226.3(11) MHz. The relatively small value of α1 as compared to theory and to the isoelectronic molecules DN+2 and DCN suggests the possibility of mixing between the (v1v2l2v3)=(1000) and (0400) vibrational states. The observation of ν1 for DCO+ means that 11 of the 12 fundamental bands have been observed for the isoelectronic family of molecular ions HCO+, DCO+, HN+2, and DN+2, leaving only ν2 of DCO+ still undetected.

The a 1Πg–a’ 1Σ−u, 0–0 band of the molecular nitrogen was observed in an electric discharge plasma of nitrogen using infrared diode laser spectroscopy at Doppler‐limited resolution. Precise values were obtained for the rotational constants and the energy separation between the two electronic states. The effect of Λ‐type doubling in the a 1Πg state was observed as small shifts of Q branch and P/R branch transitions to higher and lower frequencies, respectively, than those expected if Λ doubling were absent.

The v2 = 1←0, 2←1, and 3←2 bands of the methyl radical were observed in the gas phase by infrared tunable diode laser spectroscopy at 606.4531, 681.6369, and 731.0757 cm−1. The observed vibration–rotation spectra were analyzed to derive precise values for the rotational constants, centrifugal distortion constants, and spin–rotation interaction constants. The absence of N = odd, K = 0 levels in the v2 = even states and of N = even, K = 0 levels in the v2 = odd states was confirmed, indicating that each vibrational state is nondegenerate. The observed band origins, when analyzed, led to a potential function for the out‐of‐plane bending vibration that has no potential hump at the planar configuration. The large negative anharmonicity of this potential was ascribed to a vibronic interaction with excited electronic states. The methyl radical was generated by a 60 Hz discharge in di‐tert‐butyl peroxide and was found to have a lifetime of about 1.4 msec; its concentration in the absorption cell was estimated to ...

The gas‐phase spectrum of BH3 was detected for the first time by diode laser spectroscopy through the observation of the ν2 band. The borane was produced by photolysis of B2H6 or BH3CO with an ArF excimer laser. The same spectrum was obtained by a discharge in a B2H6 and He mixture. Line assignments were made for the Q‐branch series with J=K of the ν2 band; effects due to Coriolis perturbations by the ν4 state were recognized.

The microwave spectrum of the trifluoromethyl radical in the ground 2A1 state has been observed by using a source frequency modulation spectrometer. The CF3 radical was generated directly in the absorption cell by a glow discharge in trifluoroacetic acid anhydride (CF3CO)2O. The observed transitions included N = 4 ← 3, 5 ← 4, and 6 ← 5, all of which are resolved into K as well as fine and hyperfine structure components. A magnetic hyperfine Hamiltonian was derived for three identical nuclei with a spin of 1/2 (the fluorine nuclei) in a doublet symmetric‐top molecule, in order to analyze the observed spectrum. Most of the hyperfine structure could be explained by considering the total nuclear spin operator I0 = JiIi, except for the K = 1 transitions; some of them were clearly resolved into doublets and the observed splittings allowed us to determine the additional dipole–dipole hyperfine interaction constant ‖ Taa−Tbb ‖. The rotational constant B0 was determined to be 10 900.9118(52) MHz, with 2.5 times th...

High-resolution infrared spectroscopy has been low in sensitivity and thus it has been almost impossible to observe vibration-rotation transitions of transient molecules. Most infrared studies of such species have thus been conducted in low-temperature inert matrices, whereby structural information has been lost to a large extent. The sensitivity has, however, recently been much improved thanks to introduction of lasers. Infrared diode laser spectroscopy, for example, now allows us to detect molecules as small in number as 1010, and has in fact been successfully applied to high-resolution spectroscopic studies of transient molecules, free radicals, and molecular ions, which were generated mainly by electrical discharges [1]. The recent development of high-power lasers such as excimer laser and carbon dioxide laser makes it possible to employ such a laser for photochemical generation of transient molecules from an appropriate precursor; an excimer laser pulse typically contains 1017 photons. In the present study infrared cw diode laser spectroscopy is used to probe the nascent distribution of photofragments, mostly transient molecules, generated by the excimer laser photolysis.

The vibration‐rotation spectrum of the PCl radical has been observed by infrared diode laser spectroscopy. The radical was generated by an ac discharge in a PCl3 and H2 mixture. The observed lines have been assigned to the v=1–0 and v=2–1 bands of P35Cl and to the v=1–0 band of P37Cl. All the observed lines were included in a least‐squares analysis, where ground‐state parameters were fixed to microwave values and isotopic relations were assumed to hold for molecular constants of the two isotopic species. The equilibrium values for vibrational changes of the rotational, the spin–spin interaction, and the spin‐rotation interaction constants have thus been determined very accurately. It was found that the sign of the αλ constant of PCl is the same as that of NCl, but is opposite to those of O2, SO, S2, and SeO.

Ground-term fine-structure levels and their magnetic-dipole (M1) transition properties of Titanium-like ions are investigated theoretically through the atomic number Z = 37–103. An anomalous stability in wavelength of J = 3–2 M1-transition reported by Feldman (1991 J. Opt. Soc. Am. B 8 3) is explained in terms of a concept of the critical atomic number beyond which the relativistic nature dominates in the corresponding fine-structure. The Tokyo-EBIT facility (1996 J. Phys. Soc. Jpn 65 3186) enabled us to observe the corresponding line in the visible range for Xe+32 and Ba+34 ions. The measured wavelengths are consistent with measurements by the NIST group (1995 Phys. Rev. Lett. 74 1716), however there remains a considerable discrepancy from present calculations.

Visible and near-UV emission lines of titaniumlike highly charged ions Sb, I, Xe, Ba, Cs, Sm, Eu, Hf, Ta, W, Re, and Pt were observed using an electron beam ion trap. The wavelengths of the magnetic dipole transitions between ground-state fine-structure levels, ${(3d}^{4}{)}^{5}{D}_{J},$ were measured for these elements. These were compared with our own theoretical values, which were obtained with an extended set of configurations, and yielded differences of less than 0.6% for the elements below $Z=60,$ and about 0.1% for those over $Z=60.$

The local spin-density functional theory with an optimized effective potential and self-interaction correction is used to study the energy structure of hollow atoms or ions in the bulk of metallic materials. The energy structure of conduction electrons in the bulk of metallic material is treated by the jellium model. Based on this method, we have studied the emit ted x-ray spectra of Arq+ hollow atoms and ions in the bulk of Ag as well as in the vacuum. By comparing the energy spectra of Arq+ hollow atoms or ions in the vacuum and in the bulk of Ag, we can illustrate the conduction electron screening effect. Our calculated x-ray spectra of Arq+ hollow atoms or ions in the bulk of Ag is in reasonable agreement with the experiment.

We have been using the Tokyo EBIT to study a wide range of electron ion interactions and to measure the energies of transitions in highly charged ions. Transition energies were investigated using visible and x-ray spectroscopy. The two electron contribution to the ground state energy of Helium-like Krypton was measured using absorption-edge spectroscopy. Dielectronic recombination processes were measured by mapping the yield of x-rays as a function of electron energy whilst the time dependence of the evolution of charge states was measured, towards the determination of ionization cross-sections. A brief review of these activities is given.

A new beam line has been constructed to make various experiments with highly charged ions produced in an electron beam ion trap. The characteristics of the beam line are reported. Ions are extracted upward into the beam line and are deflected horizontally and analyzed for the charge states by a double-focusing magnet. To obtain sufficient intensity, several electrostatic lenses are located. A quadrupole lens is used to correct the distorted beam shape before an entrance slit of the magnet. Ions are accelerated during the passing of the analyzing magnet to obtain the higher mass resolution. Trajectories were calculated by a ray-tracing program and matrix multiplication for lens actions. Preliminary results are shown here for investigation of characteristics of extracted ions.

We are using the Tokyo electron beam ion trap (Tokyo-EBIT) to study a wide range of the physics of highly charged ions. Transition wavelengths have been investigated using visible and x-ray spectroscopy. The charge-state distributions of the extracted ions from the trap are shown for the different experimental conditions. Ionization cross sections are measured by observing the time dependence of the charge state evolution in the extracted ions. A brief introduction of the recent studies is given.

The pure rotational spectrum of the CCO radical in the /sup 3/..sigma../sup -/ ground electronic state has been observed in the laboratory in the region 45-185 GHz. The radical was generated in a 3.5 m long free space absorption cell by a DC glow discharge in carbon suboxide (C/sub 3/O/sub 2/). Seven rotational transitions of Nn = 2reverse arrow1 to 8reverse arrow7 in each triplet sublevels were precisely measured and the observed frequencies were least-squares analyzed to obtain molecular constants.

The SiH3 radical is an important precursor in amorphous silicon thin film formation, but its density in silane plasma has never been measured. In this work, we have developed a method for measuring the SiH3 radical density using an infrared diode laser absorption method and have determined the density in a pulsed SiH4/H2 plasma.

By using infrared diode laser absorption spectroscopy, the rotational temperature and the number density of the SiH3(X̃2A1) radical were measured in a pulsed SiH4/H2 discharge. The decay of the absorption intensity was also measured as a function of the filling gas pressure for the line Q(6, 6)(1- ← 0+) of the SiH3 ν2 fundamental band to determine the effective diffusion coefficients (D(SiH3 in H2) and D(SiH3 in SiH4)) and the reaction rate constant (k) of the SiH3 radical.

A change of discharge current is observed in CO2 plasma by irradiation with a Q-switched CO2 laser. It is elucidated that the increase of the discharge current just after the incidence of laser pulse is a correlated effect with an amplification mechanism of the laser pulse power. Evidence is also presented to support an interpretation that the rise and decay times of the current change produced by the laser pulse are effective measures of the relaxation times of the vibrational levels (10°0) and (00°1) of CO2 molecules in plasma. The effect of foreign gases is also examined.