Systematic mapping of high-lying even-parity levels (low-lying configurations) of the samarium atom below the first ionization potential was carried out with a two-step photoexcitation and photoionization method; Five hundred seventy-one new energy levels were discovered in the region 34 850-45 300 cm(-1), and an unambiguous assignment of angular momenta was given to most of the energy levels in accordance with the electric dipole selection rules. (C) 2000 Optical Society of America [S0740-3224(00)01509-5].

Two-colour two-step resonance ionization mass spectrometry is employed to observe the even-parity Rydberg levels with unique angular momentum J = 1. The bound and autoionizing Rydberg series converge at three different ionic states of samarium (Sm), namely, 4f6 (7F) 6s [8F1/2], 4f6 (7F) 6s [8F3/2] and 4f6 (7F) 6s [8F5/2]. Apart from the Rydberg levels, 80 new autoionizing energy levels with total angular momentum J = 1 are also discovered. Analyses of the Rydberg series lead to a more precise determination of the first ionization potential of atomic Sm. The value of the ionization potential obtained is 45 519.64±1.39 cm-1.

Odd-parity energy levels of the neutral europium atom (Eu I) have been investigated by employing both single-colour and two-colour stepwise laser excitation using the technique of resonance ionization spectroscopy in a heat-pipe thermionic diode system. Fifty-two new odd-parity energy levels of Eu I have been found in the energy region 40 575 - 43 410 . The J values for most of these new energy levels have been assigned unambiguously. In addition to this, 19 odd levels which were reported earlier, in the region of our present study, have also been investigated; the assignments of J values to nine of these levels have been confirmed and four levels, which had no unique J assignments, have been assigned definite J values.

Resonance ionization mass spectrometry is applied to investigate high-lying even-parity states of Sm i. Eighty-six even-parity states of Sm i are discovered in the region 32 950–36 000 cm−1. Absolute energies of these states are measured with an uncertainty of ±0.3 cm−1, and total angular momenta are uniquely assigned for most of them.

Silver dimers formed in a seeded supersonic argon beam are examined with two laser spectroscopic methods. Excitation fluorescence spectra of the A-X system excited with a narrow band cw dye laser yield accurate constants of the X 1Σg+ and the A 1Σu+ state. From isotope selective resonant two-photon ionization spectra of the B-X and the E-X system excited by a pulsed dye laser and monitored with a time-of-flight mass spectrometer, improved vibrational constants and rotational constants of the B 1Πu and the E 1Πu state are derived. Rotational constants of the C and the D state could be determined from the spectral separations between bandhead and band origin in partly rotationally resolved bands. Autoionizing Rydberg states of Ag2 are stepwise excited with two pulsed dye lasers in two resonant steps. From the convergence limits of different Rydberg series converging towards different vibrational levels v+ in the X 2Σg+ ground state of Ag2+ the rotational constants of the ion ground state and the adiabatic ionization potential IP(Ag2+)=61 747±4 cm−1 could be accurately determined.

With time-resolved spectroscopy of the fluorescence transitions 23∏g(ω) →1 3∑u radiative lifetimes τ(ω), quenching cross sections α(ω) and the population mechanisms of the 2 3∏g (ω=0, 1, 2) states under optical excitation of levels in the 3 1∑u state have been determined. The results for the different ω components are: τrad(ω) = 20–22 ns, α(ω) = 685–880 Å2.

Silver dimers Ag2 formed in a seeded supersonic argon beam are excited into autoionizing Rydberg levels by resonant two-step transitions with two pulsed dye lasers. The three isotopes of Ag+2 are separated by a time of flight mass spectrometer. From the convergence limits of different Rydberg series converging towards different vibrational levels ν+ in the X 2Σ+g ground state of Ag+2 the vibrational constants of the ion ground state and the adiabatic ionization potential IP(Ag+2) = 61747 ± 4 cm−1 could be accurately determined.

Single colour three photon resonant ionization (2 + 1) is observed in atomic potassium vapour in a heat pipe oven using an excimer laser pumped dye laser. Using wavelengths between 570 nm and 603 nm various2S and2D Rydberg states are populated by two photon excitation. Third photon of the same wavelength ionizes the atoms. Rydberg states up ton ⋍ 50 are observed. Electric field as low as 1 V/cm causes extensive Stark mixing of the states. This results in progressively higher three photon ionization signals via the perturbed2P and2F Rydberg states. The three photon ionization process is studied using both linearly and circularly polarized incident light. The experiment shows qualitatively that the2P Rydberg states are perturbed primarily by the2D states in the prescence of an external electric field and to a much smaller extent by2S states. This is also explained theoretically by calculating the Stark mixing coefficients under the Bates and Daamgard (1949) approximation. Implication for a similar effect in other alkali elements is discussed.

A 1Σ u + -X 1Σ g + emission in Na2 is observed following excitation ofB 1π u by various lines of an argon ion laser. The excitation energy ofB 1π u is collisionally transferred to the (2)1Σ g + which then radiatively populates theA 1Σ u + state. The Na vapour is contained in a stainless steel crossed heat pipe with Ar buffer gas and temperature around 600°C. For all laser lines except 4579 Å, the coarse features ofA-X emission are independent of the laser wavelength. However, at high resolution the finer differences between different laser line excitation are explained. Variousv′-v″ transitions in this emission are identified. Computer simulation is presented to help explain some features of this emission.

The third positive system (b3Σ+-a3Πr) and the three Kaplan bands of 12C16O occurring in the spectral region 2500–3830 Å are reinvestigated. In addition to the previously known bands, five new bands of 12C16O are observed. Kaplan bands and the five new bands are now assigned as the ν″ progression with ν′ = 2 (ν″ = 0 to 3 and 5 to 8) of the third positive system. The corresponding bands of 13C18O are also observed for the first time. The new vibrational assignments of 12C16O are confirmed from the calculated Franck-Condon factors and the data obtained for the bands of 13C18O. The derived molecular constants (in cm−1) for the b3Σ+-a3Πr system of 12C16O are νe=34 999.79±1.6ω′e=2333.90±2.1; ω″e=1738.26±0.6; ω′eχ′e=58.64±0.7ω″eχ″e=14.25±0.1. The corresponding constants of 13C18O are νe=35 000.31±2.0ω′e=2220.09±2.6; ω″e=1655.29±0.7; ω′eχ′e=52.19±0.8ω″eχ″e=12.82±0.1. The identification of the ν = 2 level of the b3Σ+ state favors the “higher” value of 89 460 cm−1 for the dissociation limit, rather than the “lower” value ≤ 88 262 cm−1, existing in the literature. The present work correctly interprets the Kaplan bands of CO after their first observation in 1930.

Laser-induced photodissociation of NaCs molecule has been observed when a mixture of Na and Cs metal vapour in a glass cell was irradiated by most of the lines of an argon ion laser. The photodissociation results in the 3P state of Na atoms which is correlated with theF 1Σ+ and G1π molecular states of NaCs. Distribution of photofragments over fine structure components 32 P 3/2 and 32 P 1/2 of Na has been studied. The ratio of intensity ofD 2 line (5890 Å) toD 1 line (5896 Å) of Na varies from around 2 at 5145 Å to about 3.5 at 4579 Å. The relative photodissociation cross-section increases monotonically as the wave-length of laser light decreases from 5145 Å to 4579 Å. It is seen that the 4579 Å photon is about 200 times more effective than the 5145 Å photon in causing the photoreaction NaCs + (Ar+ photon) → Na*(3P) + Cs(6S).

Fluorescence in the B 3 Pi (0+u)-X 1 Sigma g+ system of I2 excited with 5145 AA radiation of an argon ion laser was recorded photoelectrically in the region 5200-8500 AA on a SPEX 0.85 m double monochromator. Using the measured intensities of P(17) rotational lines of thirty-eight ( nu '=43, nu ") bands and the Franck-Condon factors based on the recent molecular data of the B and X states, the variation of the square of the electron transition moment, mod M(R) mod 2, with R centroid in the range R=2.65-3.09 AA was studied. It was noticed that the electronic transition strength has a maximum value at R=2.83 AA and is represented by the relation mod M(R) mod 2=constant(-500.358+377.125R-38.483R2-25.429 R3+4.9831R4). Present results are discussed in relation to those obtained from earlier studies.

The Ångström (B1Σ+-A1Π) band system of the 13C18O molecule, excited in a hollow-cathode discharge tube, has been observed in the region 4100–6500Å. All the eight bands of the system, viz., 1-0, 1-1, 0-0, 0–1, 0–2, 0–3, 0–4, and 0–5 were photographed under high resolution and their rotational analyses, except for the apparently complex 0-0 band, have been carried out. Vibrational constants of the B and A states have been obtained from the band origin data. The derived molecular constants (in cm−1, except re in Å) of the B-A system of13C18O are ωeωeXeBeαere(Å)B1∑+2012.9712.951.7805(4)0.0219(6)1.1198A1II1444.4915.731.4660(5)0.0201(1)1.2350 From the perturbations observed in the vibrational levels υ = 0, 3,and 5 of state A, it is found that the υ = 0 level is perturbed by the υ = 1 level of e3Σ− and the υ = 3 and 5 levels are perturbed by the υ = 13 and 16 levels respectively, of a′3Σ+.

$^{1}$L. Brewer and J. Tellinghuisen, J. Chem. Phys. 56, 3929-3938 (1972). $^{2}$J.B. Koffend, R. Bacis and R.W. Field, J. Chem, Phys, 70, 2366-2372 (1979). $^{3}$T.K. Balasubramanian, G.L. Bhale. M.N. Dixit and N.A. Marasimham, J. Mol. Spectrose. 88, 259-263 (1981). $^{\ast}$ G.L. Bhale is on leave from the Spectroscopy Division, Bhabha Atomic Research Centre, Bombay, India.

Chemischer InformationsdienstVolume 12, Issue 48 Physical Inorganic Chemistry ChemInform Abstract: INTENSITY MEASUREMENT OF LASER-EXCITED FLUORESCENCE IN THE B3ΠU(0+)-X1ΣG+ SYSTEM OF DIATOMIC IODINE T. K. BALASUBRAMANIAN, T. K. BALASUBRAMANIANSearch for more papers by this authorG. L. BHALE, G. L. BHALESearch for more papers by this authorM. N. DIXIT, M. N. DIXITSearch for more papers by this authorN. A. NARASIMHAM, N. A. NARASIMHAMSearch for more papers by this author T. K. BALASUBRAMANIAN, T. K. BALASUBRAMANIANSearch for more papers by this authorG. L. BHALE, G. L. BHALESearch for more papers by this authorM. N. DIXIT, M. N. DIXITSearch for more papers by this authorN. A. NARASIMHAM, N. A. NARASIMHAMSearch for more papers by this author First published: December 1, 1981 https://doi.org/10.1002/chin.198148002AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume12, Issue48December 1, 1981 RelatedInformation

Fluorescence was excited in the B3Πu(0+)-X1Σg+ system of diatomic iodine by means of the 5145-Å line of an Ar+ laser and the 6328-Å line of a HeNe laser. The resulting spectrum was recorded on a SPEX double monochromator and a quantitative measurement of the intensities was carried out. The variation of the electronic transition moment M(R) with R centroid observed by us shows a behavior similar to what has been reported earlier.