E.J. van Duijn

Frequency metrology on the EF (1)Sigma(+)(g)<- X (1)Sigma(+)(g)(0,0) transition in H2, HD, and D2

We present a frequency metrology study on the lowest rotational levels of the hydrogen EF Σg+1 ←X Σg+1 (0,0) two-photon transition near 202 nm. For this purpose, the fourth harmonic of an injection-seeded titanium:sapphire pulsed oscillator is employed in a Doppler-free REMPI-detection scheme on a molecular beam of hydrogen. A frequency comb laser is used to perform the absolute frequency calibration on the continuous-wave (CW) laser that injection-seeds the oscillator. Chirp-induced frequency differences between the output of the pulsed oscillator and the seeding light are monitored on-line, while possible systematic shifts related to the AC-Stark and Doppler effects are addressed in detail. The transition frequencies of the Q (0) to Q (2) lines in H2 and D2, and the Q (0) and Q (1) lines in HD are determined with an absolute accuracy at the 10-9 level.

A narrow-band injection-seeded pulsed titanium : sapphire oscillator-amplifier system with on-line chirp analysis for high-resolution spectroscopy

A narrow-band tunable injection-seeded pulsed titanium:sapphire laser system has been developed for application in high-resolution spectroscopic studies at the fundamental wavelengths in the near infrared as well as in the ultraviolet, deep ultraviolet, and extreme ultraviolet after upconversion. Special focus is on the quantitative assessment of the frequency characteristics of the oscillator-amplifier system on a pulse-to-pulse basis. Frequency offsets between continuous-wave seed light and the pulsed output are measured as well as linear chirps attributed mainly to mode pulling effects in the oscillator cavity. Operational conditions of the laser are found in which these offset and chirp effects are minimal. Absolute frequency calibration at the megahertz level of accuracy is demonstrated on various atomic and molecular resonance lines.

Deep-ultraviolet cavity ringdown spectroscopy

The sensitive optical detection technique of cavity ringdown spectroscopy is extended to the wavelength range 197-204 nm. A novel design narrowband Fourier-transform-limited laser is used, and the technique is applied to gas-phase extinction measurements in CO2, SF6, and O2. Further demonstration of the system capabilities is given in high-resolution recordings of the Schumann-Runge (0, 0), (1,0), and (2, 0) bands in O2.

Production of narrowband tunable extreme-ultraviolet radiation by noncollinear resonance-enhanced four-wave mixing

Fourier-transform-limited extreme-ultraviolet (XUV) radiation (bandwidth approximately < 300 MHz) tunable around 91 nm is produced by use of two-photon resonance-enhanced four-wave mixing on the Kr resonance at 94 093 cm(-1). Noncollinear phase matching ensures the generation of an XUV sum frequency 2 omega1 + omega2 that can be filtered from auxiliary laser beams and harmonics by an adjustable slit. Application of the generated XUV light is demonstrated in spectroscopic investigations of highly excited states in H2 and N2.

Third-harmonic generation of a continuous-wave Ti:Sapphire laser in external resonant cavities

An all-solid-state tunable continuous-wave (cw) laser operating near 272 nm with a bandwidth Γ≈3 MHz has been developed. The third harmonic of light from a single-cw Ti:Sapphire laser has been generated using two external enhancement cavities. An output power of 175 mW has been produced, corresponding to an overall conversion efficiency of 8%.

A Rayleigh-Brillouin scattering spectrometer for ultraviolet wavelengths

A spectrometer for the measurement of spontaneous Rayleigh-Brillouin (RB) scattering line profiles at ultraviolet wavelengths from gas phase molecules has been developed, employing a high-power frequency-stabilized UV-laser with narrow bandwidth (2 MHz). The UV-light from a frequency-doubled titanium:sapphire laser is further amplified in an enhancement cavity, delivering a 5 W UV-beam propagating through the interaction region inside a scattering cell. The design of the RB-scattering cell allows for measurements at gas pressures in the range 0-4 bars and at stably controlled temperatures from -30 °C to 70 °C. A scannable Fabry-Perot analyzer with instrument resolution of 232 MHz probes the RB profiles. Measurements on N(2) and SF(6) gases demonstrate that the high signal-to-noise ratio is achievable with the instrument at the 1% level at the peak amplitude of the scattering profile.

Hyperfine structure and isotope shift of transitions in Yb I using UV and deep-UV cw laser light and the angular distribution of fluorescence radiation

Using the third harmonic of a cw titanium:sapphire laser, the hyperfine structure (HFS) and isotope shift (IS) of three deep-UV transitions of neutral Yb have been measured for the first time. By exploiting the angular distribution of fluorescence radiation, accurate and complete results are obtained for the HFS and IS of the 398.8 nm transition of Yb. From the measured data, normal and specific mass shift as well as field shift values for all transitions considered have been derived.

Frequency metrology on the Mg 3s{sup 2} {sup 1}S{yields}3s4p {sup 1}P line for comparison with quasar data

We report a frequency metrology study on the

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\mathrm{Mg}\phantom{\rule{0.3em}{0ex}}3{s}^{2}\phantom{\rule{0.2em}{0ex}}^{1}S\ensuremath{\rightarrow}3s4p\phantom{\rule{0.2em}{0ex}}^{1}P

3s4p P-1 line for comparison with quasar data

transition near