One- and two-color two-photon resonance enhanced multiphoton ionization spectroscopy of the d 1Σ+ state of NH

Rydberg excited states of the OCS molecule in the energy range 70500-86000 cm Ϫ1 have been investigated via the two and three photon resonance enhancements they provide in the mass resolved multiphoton ionization ͑MPI͒ spectrum of a jet-cooled sample of the parent molecule. Spectral interpretation has been assisted by companion measurements of the kinetic energies of the photoelectrons that accompany the various MPI resonances. The present study supports the earlier conclusions of Weinkauf and Boesl ͓J. Chem. Phys. 98, 4459 ͑1993͔͒ regarding five Rydberg origins in the 70500-73000 cm Ϫ1 energy range, attributable to, respectively, states of 3 ⌸, 1 ⌸, 3 ⌬, 1 ⌬ and 1 ⌺ ϩ symmetry arising from the 4p←3 orbital promotion. We also identify a further 21 Rydberg origins at higher energies. These partition into clumps with quantum defects ca. 3.5 and 4.5, which we associate with the orbital promotions np←3 (nϭ5,6), and others with near integer quantum defect which are interpretable in terms of excitation to s,d and ͑possibly͒ f Rydberg orbitals. We also identify MPI resonances attributable to CO(X 1 ⌺ ϩ ) fragments and to S atoms in both their ground ( 3 P) and excited ( 1 D) electronic states. Analysis of the former resonances confirms that the CO(X) fragments resulting from one photon dissociation of OCS at excitation wavelengths ca. 230 nm are formed with a highly inverted, bimodal rotational state population distribution, whilst the latter are consistent with previous reports of the wavelength dependence for forming ground and excited state S atoms in the near uv photolysis of OCS.

Section: Methodsmentioning

confidence: 99%

Resonance enhanced multiphoton ionization spectroscopy of carbonyl sulphide

Morgan

Orr‐Ewing

Ascenzi

et al. 1996

“…Both experiments have been described in detail previously [51][52][53][54] so only brief summaries of the two experimental methods are given here.…”

Section: Methodsmentioning

confidence: 99%

Resonance enhanced multiphoton ionization spectroscopy of carbon disulphide

Morgan

Baldwin

Orr‐Ewing

et al. 1996

Rydberg excited states of the CS 2 molecule in the energy range 56 000-81 000 cm Ϫ1 have been further investigated via the two and three photon resonance enhancements they provide in the mass resolved multiphoton ionization ͑MPI͒ spectrum of a jet-cooled sample of the parent molecule. Spectral interpretation has been aided by parallel measurements of the kinetic energies of the photoelectrons that accompany the various MPI resonances. Thus we have been able to extend, and clarify, previous analyses of the tangled spin-orbit split vibronic structure associated with the

“…A more complete review of the previous work on electronic spectroscopy can be found in our previous papers. 2,3 Recent experimental [4][5][6][7][8][9][10][11][12][13][14][15][16] and theoretical 17-23 studies have been motivated by applications in astrophysics, [24][25][26][27][28][29][30][31][32][33][34] atmospheric science 35 and chemistry. [36][37][38][39][40][41][42][43] There have been several infrared and far-infrared studies of NH aimed at extracting precise molecular and hyperfine constants in the ground state.…”

Section: Introductionmentioning

confidence: 99%

Infrared emission spectroscopy of NH: Comparison of a cryogenic echelle spectrograph with a Fourier transform spectrometer

Ram

Bernath

Hinkle

1999

The high-resolution emission spectrum of NH has been observed in the near infrared using a Fourier transform spectrometer ͑FTS͒ and a cryogenic echelle spectrograph ͑called Phoenix͒ at the National Solar Observatory at Kitt Peak. By using a large format InSb array detector, the newly constructed Phoenix is calculated to offer a large increase in sensitivity over a Fourier transform spectrometer for measurements near 5 m ͑2000 cm Ϫ1 ͒. In order to test the performance of Phoenix, we recorded vibration-rotation emission spectra of the free-radical NH. The infrared bands of NH were produced in a microwave discharge of a mixture of NH 3 and He. The rotational structure of five bands, 1-0, 2-1, 3-2, 4-3, and 5-4 in the 2200-3500 cm Ϫ1 region has also been measured using two FTS spectra. An analysis of these bands combined with the previous electronic, vibrationrotation, and pure rotation measurements provides improved molecular constants for the ground electronic state. In particular, we have extended the range of measured J values so that the new constants are suitable for predicting line positions in high-temperature sources such as stellar atmospheres and flames. A comparison of the Phoenix spectra with the FTS spectra confirms the higher sensitivity of the Phoenix spectrometer. The relative advantages and disadvantages of instruments like Phoenix are discussed. Although designed for astronomical work, cryogenic echelle spectrographs have applications in the ultrasensitive detection of molecules in chemical physics.