J. H. Glownia

160-fsec XeCl excimer amplifier system

An amplifier system based on XeCl gain modules, which, generates bandwidth-limited, 160-fsec, 308-nm, 12-mJ pulses, is described. The UV seed pulses are derived from a colliding-pulse mode-locked laser system.

Femtosecond transition‐state absorption spectroscopy of Bi atoms produced by photodissociation of gaseous Bi2 molecules

Femtosecond transition‐state absorption spectroscopy has been performed on Bi atoms produced by the 308 nm photodissociation of Bi2 molecules contained in bismuth vapor. The transient spectra obtained are all clearly identifiable as atomic, yet they display striking asymmetries in line shapes and enhancements in intensity that clearly demonstrate that they are spectral signatures of atoms still in the force fields of their receding partners.

Subpicosecond uv kinetic spectroscopy: Photolysis of thallium halide vapors

Abstract The formation of Tl atoms resulting from subpicosecond UV (308, 248.5 nm) photolysis of TlCl and TlI vapors is probed via subpicosecond UV kinetic absorption spectroscopy. Unusual line shapes are observed for a period lasting roughly 1 ps, from the moment the atomic transition first appears, to the point at which the final, asymptotic, line shape is attained. These spectra are explained in terms of a model based upon the transient behavior of the polarization induced by the probe continuum pulse as it interacts with a growing population of two-level atoms whose resonance frequencies shift in time.

Classical model of femtosecond time-resolved absorption spectra of dissociating molecules

We present a simple classical model for understanding time‐resolved absorption spectra of molecules that are in the process of dissociating. The model applies to absorption spectra that are obtained by measuring the spectral power density of an ultrafast, continuum probe pulse after transmission through the sample. We show that the classical model can yield results in good agreement with quantum‐mechanical wave packet propagation calculations. In a close analogy with collisional line broadening, the time‐resolved absorption spectra are shown to have an impact region near the separated‐atom transition frequency and a far‐wing region. The impact region is due to radiation emitted after the molecule has separated into atomic fragments, and the far‐wing region is due to radiation emitted during the time of strong molecular interaction. The spectrum in the impact region depends upon an effective phase shift for a ‘‘partial’’ collision, which begins at the time that the probe pulse sweeps through the molecular ...

Amplification of 193-nm femtosecond seed pulses generated by third-order, nonresonant, difference-frequency mixing in xenon

Third-order, nonresonant, difference-frequency (2ω1 − ω2) mixing in Xe gas was used to generate femtosecond-time-scale UV pulses, tunable near 193 nm. Subsequent amplification of these pulses in an ArF excimer gain module led to the production of ≃300-fs, ≃300-μJ optical pulses at 193 nm.

56.3: Development of One Drop Fill Technology for AM‐LCDs

A new cell process for TFT-LCDs which integrates the liquid crystal (LC) injection with the glass substrate assembly process has been developed and has similarities to that previously reported for passive LCDs. In this process LC is applied in droplets directly onto the glass substrate, and results in reduced LC waste, reduction of fabrication time, and overall process simplification. With this technology, we fabricated 22 inch diagonal, high-resolution products and achieved better cell gap uniformity and fast (16.7 ms) time response for the in-plane switching (IPS) mode LCDs.

Nonlinear spectroscopy in astronomy: assignement of diffuse interstellar absorption bands to L(α) -induced, two-photon absorption by H2 molecules

Abstract All (twelve) optical diffuse interstellar absorption bands appearing in the interval 768.0–788.0 nm are assigned on the basis of a nonlinear effect: Lyman-alpha-driven, resonantly enhanced two-photon absorption by hydrogen molecules located near H II regions of young, hot stars.

Subpicosecond IR transient absorption spectroscopy: measurement of internal conversion rates in DABCO vapor

Abstract An apparatus combining subpicosecond 248.5 nm pump pulses with a time-resolved subpicosecond broadband infrared absorption spectroscopy probe has been utilized to measure an internal conversion rate in 1,4-diazabicyclo[2.2.2]octane vapor. A subpicosecond (⪅ 500 fs) internal conversion rate has been determined.

A femtosecond‐time‐scale photolysis study of vapor‐phase GaCl

Time‐resolved absorption spectra are recorded for Ga atoms produced by the photolytic action of 300 fs, 248.5 nm laser pulses on gas‐phase GaCl molecules. Photodissociation of GaCl at 248.5 nm produces both ground‐state (2P1/2) and spin–orbit‐excited (2P3/2) Ga atoms, resulting in strong transient‐absorption features at 403.3 and 417.2 nm, respectively. The experimental spectra are analyzed to obtain the kinetic energy of the photofragments, which is estimated to be ≂0.08 eV for both channels. The analysis suggests that the dissociation limits are (1) Ga 2P1/2+Cl* 2P1/2 for the 403.3 nm channel; and (2) Ga* 2P3/2+Cl 2P3/2 for the 417.2 nm channel. From these results, a new estimate for the dissociation energy of GaCl is obtained: D00=4.80±0.03 eV.

An optical scheme for enhancing the performance of theF2 (157 nm) laser; A possibleF2 two-photon femtosecond pulse generator

We have very recently begun to experimentally test a simple scheme for enhancing the efficiency of a pulsedF2 laser that our group proposed several years ago. This scheme involves the use of a pulsed nanosecond-time-scale infrared laser to deplete the terminal state of anF2 (157 nm) laser in order to enhance its performance. If the scheme should prove to be workable, this would imply that a cw two-photon UV femtosecond pulse generator might be constructed on the basis ofF2 transitions.