Zhuan Liu

Infrared laser spectroscopy of the A 2Πu←X 2Σ+g system of the Si−2 anion

Two bands of the A 2Πu←X 2Σ+g transition of Si−2 lying in the mid‐infrared region have been detected using diode laser velocity modulation spectroscopy. The anion was generated in an air cooled low pressure ac discharge through mixtures of silane and hydrogen, and 130 lines of the (1,0) and (2,0) bands lying between 670 and 810 cm−1 and 1200 to 1340 cm−1 respectively were measured and assigned. A fit to standard Hamiltonians for 2Σ and 2Π states yielded the most precise spectroscopic constants so far obtained for the anion. These have been used to derive several equilibrium parameters for the A state. The equilibrium internuclear distance of the A state is re=2.182986(16) A. The fine structure and equilibrium parameters are compared with earlier low resolution results and with ab initio calculations on Si−2.

Infrared laser absorption spectroscopy of rotational and vibration rotational transitions of HeH+ up to the dissociation threshold

Many high J pure rotational transitions of 4HeH+ up to the dissociation threshold have been measured by infrared diode laser absorption spectroscopy between 590 and 920 cm−1 in an air cooled H2/He discharge. Additional centrifugal distortion terms up to J12 have been included in the rotational Hamiltonian to fit these transitions. Ten new vibration rotational transitions have also been detected in the same spectral region, arising from both low (v=1,2) and high (v=4–7) vibrational states. Some of the transitions involving high v (v=6,7) are observed as stimulated emission signals. The measured rotational transitions are in excellent agreement with ab initio calculations based on the form of the adiabatic potential model developed by Fournier and Richard.

Infrared laser velocity modulation spectrum of the ν3 fundamental band of HBCI

The infrared spectrum of the ν3 fundamental band of HBC1+ has been observed using the velocity modulation detection technique. The ion was produced in an ac glow discharge containing a mixture of H2 and BC13. Thirty-two transitions of the fundamental band of the most naturally abundant isotopomer, H11B35C1+, between 1105 and 1170cm−1 have been assigned. The ν3 band origin and rotational constants have been determined to be ν0 = 1121.5677(20)cm−1, B 0 = 0.63089(23)cm−1 and B 1 = 0.62699(21)cm−1. A second series of lines have been attributed to the H11B37C1+ isotopomer, although it has not been possible to make an unambiguous J assignment of these lines.

Infrared laser velocity modulation spectrum of the ν3 fundamental band of HBBr

The infrared absorption spectrum of the ν3 (B–Br stretching) mode of HBBr+ has been observed using a tunable diode laser and velocity modulation spectroscopy. The ion was formed in an ac glow discharge through a flowing mixture of H2 and BBr3. Thirty-three transitions of H11B79Br+ and the same number of lines of the H11B81Br+ isotopomer have been assigned. The band origins and rotational constants are H11B79Br+: ν0=937.5696(13) cm−1, B0=0.461 822(42) cm−1, and B1=0.459 254(41) cm−1. H11B81Br+: ν0=936.0554(11) cm−1, B0=0.460 330(45) cm−1, and B1=0.457 778(43) cm−1. Ab initio calculations of the band origins and the internuclear distances have been performed using the GAUSSIAN 94 package. The calculated values are in highly satisfactory agreement with the experimental results.

Infrared laser spectrum of high J pure rotational transitions of 4HeD

Abstract Many high J pure rotational lines of HeD + in the mid-infrared region up to and above the asymptotic dissociation threshold have been detected in a D 2 /He ac glow discharge. Eighteen transitions belonging to the v =0 and v =1 levels were identified, including two bound-to-quasibound and one quasibound-to-quasibound transition. The highest quasibound level involved in the observed spectrum ( v =0, J =34) is over 2000 cm −1 above the dissociation limit. A least-squares fit of the data to the rotational term expression of a linear 1 Σ + molecule yielded spectroscopic constants for HeD + up to the distortion constant N v .

Diode laser absorption spectroscopy of the ν 2 fundamental band of propadienone formed in a pyrolysis jet

A rotationally resolved infrared spectrum of the transient molecule propadienone has been recorded in a low temperature jet using diode laser absorption spectroscopy. The molecule was generated by pyrolysis of acrylic anhydride. The spectrum arises from the intense C–O stretching mode of the molecule and several series of lines were identified using Loomis Wood plots. The most prominent series on the high frequency side of the band origin consists of both a- and b-type transitions.