## 1 Introduction  
In real-world scenarios, the fast and selective detection of security-relevant substances can be crucial to ensure the most appropriate decision is taken as a foundation for further tactical procedures and minimization of risk for first responders and the civil population. In addition to other approaches like ion mobility spectrometry, mass spectrometry (MS) has been proven as a powerful and versatile technique to detect such substances. There are some MS techniques that should be mentioned, especially when focusing on explosives. In particular, gas chromatography coupled to mass spectrometry (GC-MS) has to be mentioned as a lab based technique and is used for more than 40 years to detect explosives and is a still improving field [1; 2; 3; 4; 5; 6]. Besides an increase of reliability due to chromatographic separation, some mass spectrometers allow selective ion fragmentation of potential target substance to prove identification. This so-called tandem mass spectrometry function increases significantly the probability of a correct positive detection result and enables a lower false alarm rate, e.g., at luggage checks on airports. Ion trap (IT) mass spectrometers equipped with different ionization techniques are commonly deployed for such tandem mass spectrometric experiments. Depending on the analytical target, most IT-MS can be equipped with different ionization techniques like electron ionization (EI), chemical ionization (CI) [7], or single photon ionization (SPI) [8]. Surface analyzing techniques allow for the observation of different potentially interesting targets in forensic science like luggage, letters, or clothes without time-consuming sample pretreatment. Direct analyses in real time (DART) [9; 10], DART-Raman combination [11], desorption electrospray ionization (DESI) [12; 13], solvent assisted desorption/ionization mass spectrometry (DI-MS) [14], or a variety of laser desorption/ionization (LDI) [15] systems are common techniques. Two of the most famous setups of these LDI systems are called matrix-assisted laser desorption/ionization (MALDI) [16; 17] and surface-assisted laser desorption/ionization (SALDI) [10; 18]. Omitting a special matrix and directly using the surface where a sample is located leads to the so called direct LDI approach. If interesting spots on bulky objects like containers, bulky luggage, or cars should be analyzed, highly mobile systems are preferable that can operate with a flexible sampling. Therefore, a separation of desorption and ionization processes can be beneficial because it allows a targeted optimization of the specific components to acquire enhanced results. One effective opportunity to realize the sampling is direct laser desorption (LD) that does not require additional media other than electricity. It is commonly used as the desorption step for various applications such as investigation of biological tissues [19; 20; 21], aerosols [22], pesticides [23], drugs [24], and explosives [25; 26]. Drugs and explosives are relevant classes in forensic science. Explosives exhibit two characteristics that complicate their detection with common approaches but improves their applicability for LD: a very low vapor pressure, e.g., RDX (hexahhydro-1,3,5-trinitro-1,3,5-triazine) has 4.4 \(\times\) 10\({}^{-9}\) mPa or HNS (hexanitrostilbene) with 6.2 \(\times\) 10\({}^{-18}\) mPa [27], and many of them are thermolabile. Some drugs also have a very low vapor pressure such as cocaine hydrochloride with 1.9 \(\times\) 10\({}^{-3}\) mPa or heroin hydrochloride with 1.2 \(\times\) 10\({}^{-3}\) mPa [28] and can be detected with this system even if they are not prone to a fast thermal degradation like explosives. By using a pulsed LD, instead of a continuous wave approach [29], thermal stress is lowered and leads to less fragmentation and better detection limits for explosives. Furthermore, a pulsed LD induces a shockwave-like ablation of the sample material from the surface and thus vapor pressure of the analyte is less crucial [29].